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On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
On Sun, 24 Aug 2025 07:36:40 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
LT is wonderful. I can evolve circuits way faster than I could do the
math myself, or beadboard.
I just used a 1000 amp pulse to evaluate part of a circuit. Can't get
that from Amazon.
I am a neural net.
72 years of training with electronics.
Of course you can't always trust the part models, or trust Spice
itself. The human instinct part is key to resolving that issue.
Don't trash your soldering iron.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
I hope that circuit design will be the last skill to fall to AI.
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
I'm desiging attenuators in my spare time. I'm using LT Spice to tune >topologies and values, and testing parts (some to destruction)
alongside.
I couldn't do the algebra to get the part values, so I sim it all.
Being constrained to parts that I have or can get wrecks a nice pure >mathematical approach.
By Monday morning we'll have about a billion 8 KW pulses pushed into a
cute little Caddock DPAK resistor. I'm Spicing attenuator circuits
using those parts, especially fast step response. They have a lot of >parasitic L and C.
I have a cookie can full of dead 20 watt and 40 watt commercial
attanuators. Our pulser kills them at apparently tiny joule and watt
levels.
On Sun, 24 Aug 2025 07:36:40 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1% >>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>>solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
LT is wonderful. I can evolve circuits way faster than I could do the
math myself, or beadboard.
I just used a 1000 amp pulse to evaluate part of a circuit. Can't get
that from Amazon.
I am a neural net.
72 years of training with electronics.
Of course you can't always trust the part models, or trust Spice
itself. The human instinct part is key to resolving that issue.
Don't trash your soldering iron.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
I hope that circuit design will be the last skill to fall to AI.
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
I'm desiging attenuators in my spare time. I'm using LT Spice to tune >>topologies and values, and testing parts (some to destruction)
alongside.
I couldn't do the algebra to get the part values, so I sim it all.
Being constrained to parts that I have or can get wrecks a nice pure >>mathematical approach.
By Monday morning we'll have about a billion 8 KW pulses pushed into a
cute little Caddock DPAK resistor. I'm Spicing attenuator circuits
using those parts, especially fast step response. They have a lot of >>parasitic L and C.
I have a cookie can full of dead 20 watt and 40 watt commercial >>attanuators. Our pulser kills them at apparently tiny joule and watt >>levels.
I have some of these, taken from the Cryo cooled super-conducting bandwidth filter:
https://panteltje.nl/pub/cryo/RF_attenuator_img_2866.jpg
Adjustable.
Average power specified as 2W.
https://www.alldatasheet.com/datasheet-pdf/pdf/335613/JFW/50R-083.html
They do have more stuff:
https://www.jfwindustries.com/product-category/manually-variable-attenuators/50-ohm-dual-rotor-attenuators/
These resistors can take a hit too:
https://panteltje.nl/pub/power_50_Ohm_termination_IXIMG_0744.JPG
Maybe put some together to make a high power attenuator?
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1% >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too
slow and fail every time. I have used El Tea Spice to draw some filter
curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why
even look for a ramp when Ohm's law applies. Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a >particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup. That likely does not take as long as spice takes. It all requires understanding and practical experience. And knowledge of how to handle a soldering iron.
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start >> >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too
slow and fail every time. I have used El Tea Spice to draw some filter
curves for stuff, but there are many simple good Linux filter programs. >> >>
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why
even look for a ramp when Ohm's law applies. Different for some high
frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test >> setup. That likely does not take as long as spice takes. It all requires
understanding and practical experience. And knowledge of how to handle a
soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit
itself.
On Sun, 24 Aug 2025 19:07:49 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1% >> >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >> >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too >> >> slow and fail every time. I have used El Tea Spice to draw some filter >> >> curves for stuff, but there are many simple good Linux filter programs. >> >>
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why >> even look for a ramp when Ohm's law applies. Different for some high
frequency stuff, but then drawing resistors in spice makes little sense. >>
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test >> setup. That likely does not take as long as spice takes. It all requires >> understanding and practical experience. And knowledge of how to handle a >> soldering iron.
We rarely build a prototype for fast stuff. Usually we go for the
final multilayer PCB and hope we can sell it.
A tiny dermeled proto can be useful for characterizing parts whose
data sheets are suspect.
I believe it was Peter Baxandall who said his circuit design was often >optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit >itself.
Was that before Spice?
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1% >>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about, can be haystacked in minutes, and the result can be measured.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
That likely does not take as long as spice takes.
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start >> >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too
slow and fail every time. I have used El Tea Spice to draw some filter
curves for stuff, but there are many simple good Linux filter programs. >> >>
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why
even look for a ramp when Ohm's law applies. Different for some high
frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test >> setup. That likely does not take as long as spice takes. It all requires
understanding and practical experience. And knowledge of how to handle a
soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit
itself.
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about, >> can be haystacked in minutes, and the result can be measured.
And only somebody as dumb as John Larkin would bother.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
Why?
That likely does not take as long as spice takes.
Pull the other leg.
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >Rogers sell. Finding a printed circuit board shop that has the right >substrates in stock isn't easy, and they charge heavily to cover the
capital cost of maintaining that stock.
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>> to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about, >>> can be haystacked in minutes, and the result can be measured.
And only somebody as dumb as John Larkin would bother.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
Why?
Capacitances, inductions, transmission line effects, reflections, etc etc.
That likely does not take as long as spice takes.
Pull the other leg.
You have no experience designing and building GHz stuff.
Using Tea Spices is a joke for that.
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which
Rogers sell. Finding a printed circuit board shop that has the right
substrates in stock isn't easy, and they charge heavily to cover the
capital cost of maintaining that stock.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>> wrote:
I believe it was Peter Baxandall who said his circuit design was often
optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit
itself.
Exactly!!!
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1% >>> >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>> >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool
proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too >>> >> slow and fail every time. I have used El Tea Spice to draw some filter >>> >> curves for stuff, but there are many simple good Linux filter programs. >>> >>
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is
to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why >>> even look for a ramp when Ohm's law applies. Different for some high
frequency stuff, but then drawing resistors in spice makes little sense. >>>
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test >>> setup. That likely does not take as long as spice takes. It all requires >>> understanding and practical experience. And knowledge of how to handle a >>> soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >>optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit >>itself.
Exactly!!!
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it.
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>> to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about, >>> can be haystacked in minutes, and the result can be measured.
And only somebody as dumb as John Larkin would bother.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
Why?
Capacitances, inductions, transmission line effects, reflections, etc etc.
That likely does not take as long as spice takes.
Pull the other leg.
You have no experience designing and building GHz stuff.
Using Tea Spices is a joke for that.
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>Rogers sell. Finding a printed circuit board shop that has the right >>substrates in stock isn't easy, and they charge heavily to cover the >>capital cost of maintaining that stock.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
On Mon, 25 Aug 2025 09:28:14 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>>> wrote:
I believe it was Peter Baxandall who said his circuit design was often
optimised by analogue computing - he built it and changed component
values to get the best performance. The best analogy was the circuit
itself.
Exactly!!!
Audio is not very quantitative. You can design it literally by ear.
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>>> wrote:
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>> Rogers sell. Finding a printed circuit board shop that has the right
substrates in stock isn't easy, and they charge heavily to cover the
capital cost of maintaining that stock.
So work on FR4. Spending big on exotic boards is seldom sensible.
Most shops have the Isola stuff available, when it matters. The Rogers
lam was like copperclad shoe leather.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
https://www.dropbox.com/scl/fi/d8zn6yca7bkun0jkj3riq/Man_Top_1.jpg?rlkey=352n236tashqclwpcn6dd2qf7&raw=1
GHz is easy; you just tune out the parasitics at your favorite
frequency.
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>>>> wrote:
<snip>
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>>> Rogers sell. Finding a printed circuit board shop that has the right
substrates in stock isn't easy, and they charge heavily to cover the
capital cost of maintaining that stock.
So work on FR4. Spending big on exotic boards is seldom sensible.
Until the FR4 screws up your edges.
Most shops have the Isola stuff available, when it matters. The Rogers
lam was like copperclad shoe leather.
Some of them are remarkably soft.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
https://www.dropbox.com/scl/fi/d8zn6yca7bkun0jkj3riq/Man_Top_1.jpg?rlkey=352n236tashqclwpcn6dd2qf7&raw=1
GHz is easy; you just tune out the parasitics at your favorite
frequency.
That doesn't make it all that easy. Happily I've been able to evade that.
DC-to-GHz is harder.
You do have to pay attention. There is enough literature on transmission >line transformers that you don't actually need to "train your instincts" >with LTSpice.
Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse >stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 (1979).
cites Matick R.E. "Transmission-line pulse transformers - theory and >applications" Proc.IEEE 56 47-62
Just as well - LTSpice wasn't around back then.
On Mon, 25 Aug 2025 09:28:14 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>> >>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>> >>>>> current source. The resulting voltage droops seriously, about 0.1% >>>> >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>> >>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>> >>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are
solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>> >>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it. >>>> >>
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too >>>> >> slow and fail every time. I have used El Tea Spice to draw some filter >>>> >> curves for stuff, but there are many simple good Linux filter programs. >>>> >>
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck
NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>> >to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining
about, can be haystacked in minutes, and the result can be measured. Why >>>> even look for a ramp when Ohm's law applies. Different for some high
frequency stuff, but then drawing resistors in spice makes little sense. >>>>
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test >>>> setup. That likely does not take as long as spice takes. It all requires >>>> understanding and practical experience. And knowledge of how to handle a >>>> soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >>>optimised by analogue computing - he built it and changed component >>>values to get the best performance. The best analogy was the circuit >>>itself.
Exactly!!!
Audio is not very quantitative. You can design it literally by ear.
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>>>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>>>>> solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>>>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it. >>>>>>
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>>> to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about,
can be haystacked in minutes, and the result can be measured.
And only somebody as dumb as John Larkin would bother.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
Why?
Capacitances, inductions, transmission line effects, reflections, etc etc.
That likely does not take as long as spice takes.
Pull the other leg.
You have no experience designing and building GHz stuff.
Using Tea Spices is a joke for that.
LT has ideal and lossy transmission lines.
I decided that I really didn't understand transmission line
transformers, so I Spiced some. It was a revelation in several ways.
As Mike says, the real value of Spice is to train your instincts. I
would add, and to do the hard arithmetic too.
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>>Rogers sell. Finding a printed circuit board shop that has the right >>>substrates in stock isn't easy, and they charge heavily to cover the >>>capital cost of maintaining that stock.
So work on FR4. Spending big on exotic boards is seldom sensible.
Most shops have the Isola stuff available, when it matters. The Rogers
lam was like copperclad shoe leather.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
https://www.dropbox.com/scl/fi/d8zn6yca7bkun0jkj3riq/Man_Top_1.jpg?rlkey=352n236tashqclwpcn6dd2qf7&raw=1
GHz is easy; you just tune out the parasitics at your favorite
frequency. DC-to-GHz is harder.
On 25/08/2025 7:31 pm, Jan Panteltje wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com> >>>>>>>> wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start >>>>>>>>> at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>>>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>>>>> solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>>>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it. >>>>>>
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a computer calculating where the ball goes.
The computer guy will be too slow and fail every time.
I have used El Tea Spice to draw some filter curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ?
Design the circuit?
;-)
And with all those ultra high level scopes and stuff, who the fuck NEEDS Tea Spices?
Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>>> to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining about,
can be haystacked in minutes, and the result can be measured.
And only somebody as dumb as John Larkin would bother.
Why even look for a ramp when Ohm's law applies.
Different for some high frequency stuff, but then drawing resistors in spice makes little sense.
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test setup.
Why?
Capacitances, inductions, transmission line effects, reflections, etc etc.
All of which are measurable and calculable
That likely does not take as long as spice takes.
Pull the other leg.
You have no experience designing and building GHz stuff.
Not strictly true. The Cambridge Instruments electron beam tester could >produce 0.5nsec long pulses of electrons. We did it by generating pair
+/-7V beam blanking voltages, both which dropped to 0V for 0.5nsec. That >pulse has a GHz component.
Using Tea Spices is a joke for that.
It was distinctly helpful. There are models available for 5GHz bandwidth >broad band bipolar transistors.
I even put together a three stage Percival distributed amplifier (but
that didn't get below 0.8nsec - sad because it used more but cheaper
bipolar transistors than the faster production version).
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>> Rogers sell. Finding a printed circuit board shop that has the right
substrates in stock isn't easy, and they charge heavily to cover the
capital cost of maintaining that stock.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
Been there. Done that. Even published - rather against my inclination,
but my co-authors wanted the publication. There the bipolar transistors
were a pair of 5GHZ BFT-95
Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse >stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 (1979).
LT has ideal and lossy transmission lines.
I decided that I really didn't understand transmission line
transformers, so I Spiced some. It was a revelation in several ways.
On 8/25/25 17:07, john larkin wrote:
[...]
LT has ideal and lossy transmission lines.
I decided that I really didn't understand transmission line
transformers, so I Spiced some. It was a revelation in several ways.
Transmission lines transformers in Spice can be surprising.
For one thing, the spice transmission line model has zero
common mode admittance, so you have to add explicit elements
if that matters to you.
Jeroen Belleman
On Mon, 25 Aug 2025 09:28:14 GMT, Jan Panteltje <alien@comet.invalid> >>wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>> >>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>> >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>> >>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>> >>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>>> >>> solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>> >>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it. >>>>> >>
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a
computer calculating where the ball goes. The computer guy will be too >>>>> >> slow and fail every time. I have used El Tea Spice to draw some filter >>>>> >> curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ? Design the circuit? ;-)
And with all those ultra high level scopes and stuff, who the fuck >>>>> >> NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>>> >to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining >>>>> about, can be haystacked in minutes, and the result can be measured. Why >>>>> even look for a ramp when Ohm's law applies. Different for some high >>>>> frequency stuff, but then drawing resistors in spice makes little sense. >>>>>
The results aren't as reliable, but you can make the point that a
particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test
setup. That likely does not take as long as spice takes. It all requires >>>>> understanding and practical experience. And knowledge of how to handle a >>>>> soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >>>>optimised by analogue computing - he built it and changed component >>>>values to get the best performance. The best analogy was the circuit >>>>itself.
Exactly!!!
Audio is not very quantitative. You can design it literally by ear.
OK, count me out, them audiophiles can hear to MHz I'v 'heard' ;-)
As I get older .. about 12 kHz is my limit ATM.
In the olden days I could hear the 15625 Hz from the horizontal output transformers of the monitors in the TV studio
and tell if a monitor was in sync - or not from the sound, without looking.
A good analog scope is a useful tool.
Audio spectrum analyzer too (test for harmonics, so test for distortion). >Good PC soundcard and some software.--- Synchronet 3.21a-Linux NewsLink 1.2
In those seventies we did Eurovision sound check by having the other country send a 1000 Hz sinewave
and then measured, with a selective voltmeter, the harmonics of that 1000 Hz. >Some math on a piece of paper to get the distortion.
It had to be below some limit..
Audio is fun, I like to listen to music.
Some very old good stuff downloaded from satellite, 1958 Johnny B. Goode
Is all over youtube too...
https://www.youtube.com/watch?v=6ROwVrF0Ceg
On 8/25/25 17:07, john larkin wrote:
[...]
LT has ideal and lossy transmission lines.
I decided that I really didn't understand transmission line
transformers, so I Spiced some. It was a revelation in several ways.
Transmission lines transformers in Spice can be surprising.
For one thing, the spice transmission line model has zero
common mode admittance, so you have to add explicit elements
if that matters to you.
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>>>> Rogers sell. Finding a printed circuit board shop that has the right >>>>> substrates in stock isn't easy, and they charge heavily to cover the >>>>> capital cost of maintaining that stock.
So work on FR4. Spending big on exotic boards is seldom sensible.
Until the FR4 screws up your edges.
Most shops have the Isola stuff available, when it matters. The Rogers
lam was like copperclad shoe leather.
Some of them are remarkably soft.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
https://www.dropbox.com/scl/fi/d8zn6yca7bkun0jkj3riq/Man_Top_1.jpg?rlkey=352n236tashqclwpcn6dd2qf7&raw=1
GHz is easy; you just tune out the parasitics at your favorite
frequency.
That doesn't make it all that easy. Happily I've been able to evade that.
DC-to-GHz is harder.
You do have to pay attention. There is enough literature on transmission
line transformers that you don't actually need to "train your instincts"
with LTSpice.
Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse
stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 (1979). >>
cites Matick R.E. "Transmission-line pulse transformers - theory and
applications" Proc.IEEE 56 47-62
Just as well - LTSpice wasn't around back then.
One thing we concluded is that we don't want to use transmission-line transformers. What we really need is wideband, isolation, and low
leakage inductance.
It's usually the low leakage inductance that coaxial or twisted-pair
or bifilar-wound transformers provide, and the txline coupling can be
an undesirable parasitic.
The only coupling that we want between windings is magnetic.
On Mon, 25 Aug 2025 16:36:21 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On Mon, 25 Aug 2025 09:28:14 GMT, Jan Panteltje <alien@comet.invalid> >>>wrote:
Jan Panteltje <alien@comet.invalid> wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed >>>>>> >>>>> current source. The resulting voltage droops seriously, about 0.1% >>>>>> >>>>> over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step >>>>>> >>>> small, my pulse gets flat.
It looks like the first step of the current source overshoots, and >>>>>> >>>> then the voltage creeps back toward right.
That's a well known problem with numerical integration. There are >>>>>> >>> solutions, but they involve adding extra steps.
Mike Englehart admitted here that LTSpice wasn't made quite as fool >>>>>> >>> proof as it might be, to let it run appreciably faster.
In my view LTSpice is much of a hype.
Have not used it in several yeas now.
All my stuff works, nearly always first time I design and build it. >>>>>> >>
I am a neural net.
72 years of training with electronics.
Me versus LTSpice is like a tennis player versus some guy with a >>>>>> >> computer calculating where the ball goes. The computer guy will be too
slow and fail every time. I have used El Tea Spice to draw some filter
curves for stuff, but there are many simple good Linux filter programs.
You could ask AI to do the simulation ? Design the circuit? ;-) >>>>>> >>
And with all those ultra high level scopes and stuff, who the fuck >>>>>> >> NEEDS Tea Spices? Games people play....
It's a lot faster and cheaper to put a circuit into LTSpice than it is >>>>>> >to put it onto a printed circuit board (and lay out the board).
I disagree, simple resistor networks, the one the OP was complaining >>>>>> about, can be haystacked in minutes, and the result can be measured. Why >>>>>> even look for a ramp when Ohm's law applies. Different for some high >>>>>> frequency stuff, but then drawing resistors in spice makes little sense. >>>>>>
The results aren't as reliable, but you can make the point that a >>>>>> >particular circuit is sub-optimal very quickly and cheaply.
Same goes for high to very high frequencies, you will HAVE to build a test
setup. That likely does not take as long as spice takes. It all requires >>>>>> understanding and practical experience. And knowledge of how to handle a >>>>>> soldering iron.
I believe it was Peter Baxandall who said his circuit design was often >>>>>optimised by analogue computing - he built it and changed component >>>>>values to get the best performance. The best analogy was the circuit >>>>>itself.
Exactly!!!
Audio is not very quantitative. You can design it literally by ear.
OK, count me out, them audiophiles can hear to MHz I'v 'heard' ;-)
As I get older .. about 12 kHz is my limit ATM.
In the olden days I could hear the 15625 Hz from the horizontal output transformers of the monitors in the TV studio
and tell if a monitor was in sync - or not from the sound, without looking.
I used to hear 22 KHz. Now I'm about 8. There's not a lot to hear
above 8 KHz.
A good analog scope is a useful tool.
I haven't used an analog scope in decades. My 11802 sampler has a CRT
display (raster scan magnetic deflection with touch screen!) but the
rest is all solid-state.
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
It all requires understanding and practical experience.
And knowledge of how to handle a soldering iron.
And time. Very high frequency circuits call for exotic substrates, which >>>>>> Rogers sell. Finding a printed circuit board shop that has the right >>>>>> substrates in stock isn't easy, and they charge heavily to cover the >>>>>> capital cost of maintaining that stock.
So work on FR4. Spending big on exotic boards is seldom sensible.
Until the FR4 screws up your edges.
Most shops have the Isola stuff available, when it matters. The Rogers >>>> lam was like copperclad shoe leather.
Some of them are remarkably soft.
You are blinded by peeseebees.
Design and build some GHz stuff and then come back.
https://www.dropbox.com/scl/fi/d8zn6yca7bkun0jkj3riq/Man_Top_1.jpg?rlkey=352n236tashqclwpcn6dd2qf7&raw=1
GHz is easy; you just tune out the parasitics at your favorite
frequency.
That doesn't make it all that easy. Happily I've been able to evade that. >>>
DC-to-GHz is harder.
You do have to pay attention. There is enough literature on transmission >>> line transformers that you don't actually need to "train your instincts" >>> with LTSpice.
Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse
stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 (1979).
cites Matick R.E. "Transmission-line pulse transformers - theory and
applications" Proc.IEEE 56 47-62
Just as well - LTSpice wasn't around back then.
One thing we concluded is that we don't want to use transmission-line
transformers. What we really need is wideband, isolation, and low
leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
Concentrate on the magnetic coupling between the windings.
Transmission line transformers are poor isolators. The capacitative
coupling between the winding is high. If you need speed and isolation
it's got to be opto-isolators.
It's usually the low leakage inductance that coaxial or twisted-pair
or bifilar-wound transformers provide, and the txline coupling can be
an undesirable parasitic.
"Bifilar windings" are twisted pair windings, and there's obviously a
lot of interwinding capacitance
The only coupling that we want between windings is magnetic.
Pity about the laws of physics.
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>[...]
wrote:
Transmission line transformers are poor isolators. The capacitative >coupling between the winding is high. If you need speed and isolation
it's got to be opto-isolators.
For coupling a kilovolt pulse into a 50 ohm load?
john larkin <jl@glen--canyon.com> wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>[...]
wrote:
Transmission line transformers are poor isolators. The capacitative
coupling between the winding is high. If you need speed and isolation
it's got to be opto-isolators.
For coupling a kilovolt pulse into a 50 ohm load?
Have you looked into constructing your own 50-ohm load in the form of a >shorted coaxial or twin transmission line made from some resistive
material such as nichrome?
If it were coaxial and made from expanded metal sheet rolled into a
cylinder, the resistance would be higher than the sheet metal alone and
the cooling would be much better. If it were twin, ordinary nichrome
wire could be used with the conductors firmly held at the correct
spacing by heat-resisting insulators. There is a considerable force >generated between parallel conductors carrying heavy current, so they
need to be restrained.
To get 50 ohms you might need a fair length but I presume this is for
your own testing purposes and you aren't intending to sell them.
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
One thing we concluded is that we don't want to use transmission-line
transformers. What we really need is wideband, isolation, and low
leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
Concentrate on the magnetic coupling between the windings.
Transmission line transformers are poor isolators. The capacitative
coupling between the winding is high. If you need speed and isolation
it's got to be opto-isolators.
For coupling a kilovolt pulse into a 50 ohm load?
It's usually the low leakage inductance that coaxial or twisted-pair
or bifilar-wound transformers provide, and the txline coupling can be
an undesirable parasitic.
"Bifilar windings" are twisted pair windings, and there's obviously a
lot of interwinding capacitance
The only coupling that we want between windings is magnetic.
Pity about the laws of physics.
Sometimes physics needs some help from design.
On Tue, 26 Aug 2025 18:06:04 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
john larkin <jl@glen--canyon.com> wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>[...]
wrote:
Transmission line transformers are poor isolators. The capacitative
coupling between the winding is high. If you need speed and isolation >>>> it's got to be opto-isolators.
For coupling a kilovolt pulse into a 50 ohm load?
Have you looked into constructing your own 50-ohm load in the form of a
shorted coaxial or twin transmission line made from some resistive
material such as nichrome?
If it were coaxial and made from expanded metal sheet rolled into a
cylinder, the resistance would be higher than the sheet metal alone and
the cooling would be much better. If it were twin, ordinary nichrome
wire could be used with the conductors firmly held at the correct
spacing by heat-resisting insulators. There is a considerable force
generated between parallel conductors carrying heavy current, so they
need to be restrained.
To get 50 ohms you might need a fair length but I presume this is for
your own testing purposes and you aren't intending to sell them.
The Caddock dpak 50 ohm resistors look very good. We banged one with a
few hundred million 600 volt pulses and its value didn't change at
all.
That's sure easy. I plan to dremel some dummy loads and see what their high-speed behavior is like.
I have some 2512 thinfilm resistors on order, ditto.
Building some mechanical thing would be a last resort. It's easy to pick-and-place parts on pc boards.
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line
transformers. What we really need is wideband, isolation, and low
leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>> transformers. What we really need is wideband, isolation, and low
leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>> transformers. What we really need is wideband, isolation, and low
leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
The usual approach is to short one winding and measure the inductance of
the other. Since the shorted winding has a finite impedance, it isn't >entirely accurate.
If you know the resistance of each winding - which you can measure
perfectly accurately at low frequencies - and the parallel capacitance
of each winding - which is lot harder to measure since the two windings >interact - most people can do better with a series of measurements at >different frequencies. You need to measure the in-phase and quadrature >components of the output signals, which is a pest.
Few bother. If you want the national standards lab take on the problem
you can buy Rayner and Kibble's "Coaxial AC Bridges" ISBN 0-85274-3989-0 >which cover's "mutual inductors" on pages 79-87. Bryan Kibble's name is >attached to the modern standard of mass - the "Kibble Balance".
https://en.wikipedia.org/wiki/Kibble_balance
He did seem to know what he was talking about.
The real problem of talking in terms of leakage inductance is that it
gives you the wrong point of view about what's going on in the
transformer, which can be decidedly complicated.
On Thu, 28 Aug 2025 02:34:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>>>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>>> transformers. What we really need is wideband, isolation, and low >>>>>>> leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
The usual approach is to short one winding and measure the inductance of
the other. Since the shorted winding has a finite impedance, it isn't
entirely accurate.
Someone said that " doesn't turn out to be a useful concept"
On 8/27/25 18:57, john larkin wrote:
On Thu, 28 Aug 2025 02:34:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>>>> transformers. What we really need is wideband, isolation, and low >>>>>>>> leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
The usual approach is to short one winding and measure the inductance of >>> the other. Since the shorted winding has a finite impedance, it isn't
entirely accurate.
Someone said that " doesn't turn out to be a useful concept"
I found the concept of leakage inductance very useful, but I did
not measure it like that. Shorting a winding isn't practical in RF >transformers where leakage inductance is in the single-digit
nanohenry range.
I would measure the high frequency cut-off using a VNA and calculate
the leakage inductance from that, then insert that into a spice
model to confirm that this indeed resulted in the measured cut-off
frequency.
There are other parasitic elements that affect upper cut-off.
I had one transformer where the leakage inductance worked out
to about 500pH. It had a bandwidth of 10kHz-6GHz. There is no
such thing as a dead short at 6GHz. You can only get so close.
Jeroen Belleman
On Thu, 28 Aug 2025 02:34:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid> >>>>>>>>> wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>>> transformers. What we really need is wideband, isolation, and low >>>>>>> leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
The usual approach is to short one winding and measure the inductance of
the other. Since the shorted winding has a finite impedance, it isn't
entirely accurate.
Someone said that " doesn't turn out to be a useful concept".
If you know the resistance of each winding - which you can measure
perfectly accurately at low frequencies - and the parallel capacitance
of each winding - which is lot harder to measure since the two windings
interact - most people can do better with a series of measurements at
different frequencies. You need to measure the in-phase and quadrature
components of the output signals, which is a pest.
Few bother. If you want the national standards lab take on the problem
you can buy Rayner and Kibble's "Coaxial AC Bridges" ISBN 0-85274-3989-0
which cover's "mutual inductors" on pages 79-87. Bryan Kibble's name is
attached to the modern standard of mass - the "Kibble Balance".
https://en.wikipedia.org/wiki/Kibble_balance
He did seem to know what he was talking about.
The real problem of talking in terms of leakage inductance is that it
gives you the wrong point of view about what's going on in the
transformer, which can be decidedly complicated.
It's easy to measure and maps directly into a Spice model.
And works.
Once the transformer is built, I generally TDR it.
Yes, we actually build transformers.
On 28/08/2025 2:57 am, john larkin wrote:
On Thu, 28 Aug 2025 02:34:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>>>> transformers. What we really need is wideband, isolation, and low >>>>>>>> leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it
directly.
How?
The usual approach is to short one winding and measure the inductance of >>> the other. Since the shorted winding has a finite impedance, it isn't
entirely accurate.
Someone said that " doesn't turn out to be a useful concept".
It's an easy measurement that doesn't give quite the right answer.
If you know the resistance of each winding - which you can measure
perfectly accurately at low frequencies - and the parallel capacitance
of each winding - which is lot harder to measure since the two windings
interact - most people can do better with a series of measurements at
different frequencies. You need to measure the in-phase and quadrature
components of the output signals, which is a pest.
Few bother. If you want the national standards lab take on the problem
you can buy Rayner and Kibble's "Coaxial AC Bridges" ISBN 0-85274-3989-0 >>> which cover's "mutual inductors" on pages 79-87. Bryan Kibble's name is
attached to the modern standard of mass - the "Kibble Balance".
https://en.wikipedia.org/wiki/Kibble_balance
He did seem to know what he was talking about.
The real problem of talking in terms of leakage inductance is that it
gives you the wrong point of view about what's going on in the
transformer, which can be decidedly complicated.
It's easy to measure and maps directly into a Spice model.
It's certainly an easy measurement. The Spice model for a mutual
inductor includes the coupling coefficient, but that scheme of shorting
one winding and measuring the residual inductance of the other doesn't
give you the coupling coefficient directly. You have to plug in more
data to get there.
And works.
Well enough, most of the time. Life gets awkward when it doesn't.
Once the transformer is built, I generally TDR it.
Doing time domain reflectometry on a transformer is kind of odd.
Do you
load the secondary with some kind of terminating resistance?
Yes, we actually build transformers.
But you much prefer to buy them off the shelf.
And when you model them
in Spice you mostly leave out the series resistance and parallel
capacitance of the windings.
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
I have a circuit that's all resistors, driven by an ideal pulsed
current source. The resulting voltage droops seriously, about 0.1%
over 100 msec.
If I turn off the initial state solution and have the supplies start
at zero, it makes a clean flat puse.
Weird.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
It's also about time steps in LT Spice. If I force the time step
small, my pulse gets flat.
It looks like the first step of the current source overshoots, and
then the voltage creeps back toward right.
On Thu, 28 Aug 2025 18:06:59 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 2:57 am, john larkin wrote:
On Thu, 28 Aug 2025 02:34:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 28/08/2025 1:36 am, john larkin wrote:
On Wed, 27 Aug 2025 17:39:31 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
On 27/08/2025 12:53 am, john larkin wrote:
On Tue, 26 Aug 2025 15:11:51 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
On 26/08/2025 2:20 am, john larkin wrote:
On Tue, 26 Aug 2025 02:12:49 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 26/08/2025 1:07 am, john larkin wrote:
On Mon, 25 Aug 2025 09:31:59 GMT, Jan Panteltje <alien@comet.invalid>
wrote:
On 25/08/2025 1:41 am, Jan Panteltje wrote:
On 24/08/2025 5:36 pm, Jan Panteltje wrote:
On 24/08/2025 9:10 am, john larkin wrote:
On Fri, 22 Aug 2025 16:53:10 -0700, john larkin <jl@glen--canyon.com>
wrote:
<snip>
One thing we concluded is that we don't want to use transmission-line >>>>>>>>> transformers. What we really need is wideband, isolation, and low >>>>>>>>> leakage inductance.
"Leakage inductance" doesn't turn out to be a useful concept.
It's how we quantify the coupling between windings. You know,
engineering.
You shouldn't. The right way to quantify coupling is to measure it >>>>>> directly.
How?
The usual approach is to short one winding and measure the inductance of >>>> the other. Since the shorted winding has a finite impedance, it isn't
entirely accurate.
Someone said that " doesn't turn out to be a useful concept".
It's an easy measurement that doesn't give quite the right answer.
Nothing gives the exact answer. One key part of engineering is knowing
what is important and what's not. If you factor in everything, you'll
get nothing done.
Are you interested in getting things done?
If you know the resistance of each winding - which you can measure
perfectly accurately at low frequencies - and the parallel capacitance >>>> of each winding - which is lot harder to measure since the two windings >>>> interact - most people can do better with a series of measurements at
different frequencies. You need to measure the in-phase and quadrature >>>> components of the output signals, which is a pest.
Few bother. If you want the national standards lab take on the problem >>>> you can buy Rayner and Kibble's "Coaxial AC Bridges" ISBN 0-85274-3989-0 >>>> which cover's "mutual inductors" on pages 79-87. Bryan Kibble's name is >>>> attached to the modern standard of mass - the "Kibble Balance".
https://en.wikipedia.org/wiki/Kibble_balance
He did seem to know what he was talking about.
The real problem of talking in terms of leakage inductance is that it
gives you the wrong point of view about what's going on in the
transformer, which can be decidedly complicated.
It's easy to measure and maps directly into a Spice model.
It's certainly an easy measurement. The Spice model for a mutual
inductor includes the coupling coefficient, but that scheme of shorting
one winding and measuring the residual inductance of the other doesn't
give you the coupling coefficient directly. You have to plug in more
data to get there.
I don't bother to compute K. I just set K=1 and add an inductor to the circuit.
Sometimes Spice seems to run faster if K=0.9999, so I might do that
too.
And works.
Well enough, most of the time. Life gets awkward when it doesn't.
Once the transformer is built, I generally TDR it.
Doing time domain reflectometry on a transformer is kind of odd.
Do you load the secondary with some kind of terminating resistance?
Granted. Play it safe and never do anything odd.
https://www.dropbox.com/scl/fi/bym3uc6x6ongshwcu8qlb/Coilcraft_PL300_planar.jpg?rlkey=wz3izrg7xbk066799nhwf6pka&raw=1
https://www.dropbox.com/scl/fi/eho2gljblcxoo631lq5dm/Coilcraft_PL300_TDR.jpg?rlkey=liidyziffsy3cavkzf9xux8hp&raw=1
Yes, we actually build transformers.
But you much prefer to buy them off the shelf.
When I can get a nice surface-mount part for 95 cents, I'd rather not
design and manufacture it.
And when you model them
in Spice you mostly leave out the series resistance and parallel
capacitance of the windings.
I leave them out when they don't matter.
Sometimes very subtle things matter in magnetics, like magnetic domain noise, magnestriction,
low-level stickiness, whatever. It's a matter of estimating magnitudes
and ignoring the tiny stuff.
