I am trying to replace my BFR193 transistors with BFR181 but they no
longer do their transistor job once I solder them. I am at Ic = 2 mA, Vce
= 3 V.
Am I the only one is this case ?
I am trying to replace my BFR193 transistors with BFR181 but they no
longer do their transistor job once I solder them. I am at Ic = 2 mA,
Vce = 3 V.
Am I the only one is this case ?
On 2/26/26 18:59, Jean-Pierre Coulon wrote:
I am trying to replace my BFR193 transistors with BFR181 but they no
longer do their transistor job once I solder them. I am at Ic = 2 mA,
Vce = 3 V.
Am I the only one is this case ?
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Jeroen Belleman
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon <coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre CoulonDo you really need 8GHz transistors? There's a hefty RC lowpass
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz
for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk >>
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >infineon models and not that simplistic mytotor model). Adding
resistance or bead to Q2 base will stop it, but you're correct - why
use these in the first place?
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre CoulonDo you really need 8GHz transistors? There's a hefty RC lowpass
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk >>>
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>infineon models and not that simplistic mytotor model). Adding
resistance or bead to Q2 base will stop it, but you're correct - why
use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman >>><jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre CoulonDo you really need 8GHz transistors? There's a hefty RC lowpass
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>>>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk >>>>
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>infineon models and not that simplistic mytotor model). Adding >>>resistance or bead to Q2 base will stop it, but you're correct - why
use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the
amp is stable with a BFR193 but not with a BFR181, which is what he observes.
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman >>>><jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>>>>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>infineon models and not that simplistic mytotor model). Adding >>>>resistance or bead to Q2 base will stop it, but you're correct - why >>>>use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the
amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman >>>><jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better >>>>>>>> chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist:
* transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>infineon models and not that simplistic mytotor model). Adding >>>>resistance or bead to Q2 base will stop it, but you're correct - why >>>>use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the
amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
Version 4.1
SHEET 1 6000 680
WIRE 608 -416 368 -416
WIRE 864 -416 608 -416
WIRE 864 -368 864 -416
WIRE 368 -336 368 -416
WIRE 608 -256 608 -416
WIRE 864 -256 864 -288
WIRE 272 -224 256 -224
WIRE 368 -224 368 -256
WIRE 368 -224 336 -224
WIRE 368 -208 368 -224
WIRE 544 -208 368 -208
WIRE 368 -160 368 -208
WIRE 608 -128 608 -160
WIRE 720 -128 608 -128
WIRE 832 -128 720 -128
WIRE -16 -112 -80 -112
WIRE 128 -112 64 -112
WIRE 208 -112 128 -112
WIRE 256 -112 256 -224
WIRE 256 -112 208 -112
WIRE 304 -112 256 -112
WIRE 608 -96 608 -128
WIRE 720 -96 720 -128
WIRE 128 -64 128 -112
WIRE -80 -48 -80 -112
WIRE 368 -32 368 -64
WIRE 608 0 608 -16
WIRE 720 0 720 -32
WIRE 720 0 608 0
WIRE 208 16 208 -112
WIRE 432 16 208 16
WIRE 608 16 608 0
WIRE 608 16 512 16
WIRE 128 32 128 0
WIRE 608 48 608 16
WIRE 608 176 608 128
WIRE 608 304 608 256
FLAG 368 -32 0
FLAG 864 -256 0
FLAG 608 304 0
FLAG 128 32 0
FLAG -80 -48 0
SYMBOL npn 304 -160 R0
SYMATTR InstName Q1
SYMATTR Value BFR181
SYMBOL res 352 -352 R0
SYMATTR InstName R9
SYMATTR Value 5.6k
SYMBOL cap 336 -240 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 0.1p
SYMBOL res 80 -128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL voltage 864 -384 R0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL npn 544 -256 R0
SYMATTR InstName Q2
SYMATTR Value BFR181
SYMBOL res 592 -112 R0
SYMATTR InstName R2
SYMATTR Value 1.8k
SYMBOL res 592 32 R0
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL voltage 608 160 R0
SYMATTR InstName V3
SYMATTR Value -5
SYMBOL cap 704 -96 R0
SYMATTR InstName C2
SYMATTR Value 100n
SYMBOL res 528 0 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 4k
SYMBOL cap 112 -64 R0
SYMATTR InstName C3
SYMATTR Value 22p
TEXT -32 384 Left 2 !.MODEL BFR181 NPN(IS=1.0519E-18 ISE=1.2603E-14 ISC=1.1195E-17 XTI=3 BF=96.461\n+ NR=0.87757 IKF=0.12146
IKR=0.24951 XTB=1.5 VAF=22.403 VAR=5.1127 VJE=0.73155\n+ VJC=1.1633 RE=2.1372 RC=2.2171 RB=9.9037 RBM=6.6315 IRB=0.00069278
CJE=1.8168f\n+ CJC=3.1969E-13 XCJC=0.082903 FC=0.99768 NF=0.90617 BR=16.504 NE=1.7631 NC=1.6528\n+ MJE=0.43619 MJC=0.30013
TF=1.7028E-11 TR=2.7449n ITF=0.0010549 VTF=0.12571\n+ XTF=0.33814 EG=1.11 VCEO=20 ICRATING=20m MFG=SIEMENS)
TEXT -80 232 Left 2 !.tran 1 startup
TEXT -80 264 Left 2 !.options plotwinsize=0
On Fri, 27 Feb 2026 11:19:44 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist: >>>>>>>> * transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p >>>>>>>>
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>> infineon models and not that simplistic mytotor model). Adding
resistance or bead to Q2 base will stop it, but you're correct - why >>>>> use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the
amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
The usual Spice models don't include package parasitics.
Lead and wirebond inductances encourage oscillation.
Many RF parts have their wirebonds specifically tuned to optimize
operation in one RF band. LDMOS for example.
Ancient TO-5 parts like 2N2219 had LONG wirebonds so a simple emitter follower would often oscillate. The fix is a 100 ohm series base
resistor to kill the Q.
On 28/02/2026 4:04 am, john larkin wrote:
On Fri, 27 Feb 2026 11:19:44 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist: >>>>>>>>> * transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p >>>>>>>>>
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>>> infineon models and not that simplistic mytotor model). Adding
resistance or bead to Q2 base will stop it, but you're correct - why >>>>>> use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still >>>>> a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the >>>> amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
The usual Spice models don't include package parasitics.
There no reason why you shouldn't add your own.
Lead and wirebond inductances encourage oscillation.
Many RF parts have their wirebonds specifically tuned to optimize
operation in one RF band. LDMOS for example.
Ancient TO-5 parts like 2N2219 had LONG wirebonds so a simple emitter
follower would often oscillate. The fix is a 100 ohm series base
resistor to kill the Q.
Why chose 100R? Cambridge Instruments engineers took to sticking a 10R >resistor in series with every DMOS gate, not because 10R was a magic
value, but because it was lot easier to change the value of that
resistor than it was to change the printed circuit layout if it hadn't
got a space for a resistor.
On 28/02/2026 4:04 am, john larkin wrote:
On Fri, 27 Feb 2026 11:19:44 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist: >>>>>>>>> * transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p >>>>>>>>>
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass
right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>>> infineon models and not that simplistic mytotor model). Adding
resistance or bead to Q2 base will stop it, but you're correct - why >>>>>> use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still >>>>> a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the >>>> amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
The usual Spice models don't include package parasitics.
There no reason why you shouldn't add your own.
Lead and wirebond inductances encourage oscillation.
Many RF parts have their wirebonds specifically tuned to optimize
operation in one RF band. LDMOS for example.
Ancient TO-5 parts like 2N2219 had LONG wirebonds so a simple emitter
follower would often oscillate. The fix is a 100 ohm series base
resistor to kill the Q.
Why chose 100R? Cambridge Instruments engineers took to sticking a 10R resistor in series with every DMOS gate, not because 10R
was a magic value, but because it was lot easier to change the value of that resistor than it was to change the printed circuit
layout if it hadn't got a space for a resistor.
--
Bill Sloman, Sydney
On Fri, 27 Feb 2026 11:19:44 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:5l72qk514j9bd6ggbkl6cdh4ua876i0dtv@4ax.com...
On Thu, 26 Feb 2026 16:44:48 -0800, john larkin <jl@glen--canyon.com>
wrote:
On Thu, 26 Feb 2026 21:20:48 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Thu, 26 Feb 2026 21:54:14 +0100, Jeroen Belleman >>>>><jeroen@nospam.please> wrote:
On 2/26/26 21:05, JM wrote:
On Thu, 26 Feb 2026 20:50:50 +0100, Jean-Pierre Coulon
<coulon@cacas.pam.obs-nice.fr> wrote:
On Thu, 26 Feb 2026, Jeroen Belleman wrote:
It's probably screaming at the top of its little voice at a few GHz >>>>>>>>> for a millisecond before giving up the ghost.
Then I need a digital scope to record the process?
Show us what you are doing, schematics and layout. We'll have a better
chance at guessing what happened.
Since I can't attach a drawing here, this is the SPICE netlist: >>>>>>>> * transimp simple
vin 20 0 ac 1
rcalib 20 1 10k
cphd 1 0 22p
q1 2 1 0 mytotor
rtransimp 1 4 4k
ccomp 2 1 .1p
vp5 10 0 dc 5
R9 10 2 5.6k
Rab 3 4 1.8k
Ca 3 4 100n
q2 10 2 3 mytotor
R11 4 11 10k
vm5 11 0 dc -5
.model mytotor npn rb=4 is=1e-14 bf=150 tf=20p cje=.5p cjc=.5p >>>>>>>>
Bye,
https://mega.nz/file/gxsERDzD#VMfGH9XRllX1gzkSb7aMcFWRcy8KTx5acn7rbONECsk
Do you really need 8GHz transistors? There's a hefty RC lowpass >>>>>>right at the input.
Jeroen Belleman
It oscillates like buggery with a BFR193 nevermind a BFR181 (using the >>>>>infineon models and not that simplistic mytotor model). Adding >>>>>resistance or bead to Q2 base will stop it, but you're correct - why >>>>>use these in the first place?
People hardly make slow transistors any more.
My go-to gumdrop NPN is a BCX70J, which has huge beta, but it's still
a couple hundred MHz. An emitter follower may well oscillate.
I mostly use mosfets, like 2N7002 or FDV301.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
Well nobody is going to manufacture something if no-one is going to
buy it. The low frequency discrete transistor market has been
shrinking for the past 30 years. We were spoiled for choice back in
the day and never knew it.
Looking closer at this chap's circuit I assume that cphd is actually
the sensor, and rcalib is for some sort of system calibration. (It
would help if people actually stated WTF they are trying to do,
especially the sensor type they are interfacing too.)
In that case modelling the input as a current source into Q1 base, the
amp is stable with a BFR193 but not with a BFR181, which is what he
observes.
If you have time can you let me know why I can't see any oscillation with the model below.
There may, of course, be many reasons. The BFR181 model (which I got from the first
search engine hit on the subject) may be inadequate or perhaps R1/C3 needs changing
as you said above.
Thanks.
Version 4.1
SHEET 1 6000 680
WIRE 608 -416 368 -416
WIRE 864 -416 608 -416
WIRE 864 -368 864 -416
WIRE 368 -336 368 -416
WIRE 608 -256 608 -416
WIRE 864 -256 864 -288
WIRE 272 -224 256 -224
WIRE 368 -224 368 -256
WIRE 368 -224 336 -224
WIRE 368 -208 368 -224
WIRE 544 -208 368 -208
WIRE 368 -160 368 -208
WIRE 608 -128 608 -160
WIRE 720 -128 608 -128
WIRE 832 -128 720 -128
WIRE -16 -112 -80 -112
WIRE 128 -112 64 -112
WIRE 208 -112 128 -112
WIRE 256 -112 256 -224
WIRE 256 -112 208 -112
WIRE 304 -112 256 -112
WIRE 608 -96 608 -128
WIRE 720 -96 720 -128
WIRE 128 -64 128 -112
WIRE -80 -48 -80 -112
WIRE 368 -32 368 -64
WIRE 608 0 608 -16
WIRE 720 0 720 -32
WIRE 720 0 608 0
WIRE 208 16 208 -112
WIRE 432 16 208 16
WIRE 608 16 608 0
WIRE 608 16 512 16
WIRE 128 32 128 0
WIRE 608 48 608 16
WIRE 608 176 608 128
WIRE 608 304 608 256
FLAG 368 -32 0
FLAG 864 -256 0
FLAG 608 304 0
FLAG 128 32 0
FLAG -80 -48 0
SYMBOL npn 304 -160 R0
SYMATTR InstName Q1
SYMATTR Value BFR181
SYMBOL res 352 -352 R0
SYMATTR InstName R9
SYMATTR Value 5.6k
SYMBOL cap 336 -240 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 0.1p
SYMBOL res 80 -128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 10k
SYMBOL voltage 864 -384 R0
SYMATTR InstName V2
SYMATTR Value 5
SYMBOL npn 544 -256 R0
SYMATTR InstName Q2
SYMATTR Value BFR181
SYMBOL res 592 -112 R0
SYMATTR InstName R2
SYMATTR Value 1.8k
SYMBOL res 592 32 R0
SYMATTR InstName R11
SYMATTR Value 10k
SYMBOL voltage 608 160 R0
SYMATTR InstName V3
SYMATTR Value -5
SYMBOL cap 704 -96 R0
SYMATTR InstName C2
SYMATTR Value 100n
SYMBOL res 528 0 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R3
SYMATTR Value 4k
SYMBOL cap 112 -64 R0
SYMATTR InstName C3
SYMATTR Value 22p
TEXT -32 384 Left 2 !.MODEL BFR181 NPN(IS=1.0519E-18 ISE=1.2603E-14 ISC=1.1195E-17 XTI=3 BF=96.461\n+ NR=0.87757 IKF=0.12146
IKR=0.24951 XTB=1.5 VAF=22.403 VAR=5.1127 VJE=0.73155\n+ VJC=1.1633 RE=2.1372 RC=2.2171 RB=9.9037 RBM=6.6315 IRB=0.00069278
CJE=1.8168f\n+ CJC=3.1969E-13 XCJC=0.082903 FC=0.99768 NF=0.90617 BR=16.504 NE=1.7631 NC=1.6528\n+ MJE=0.43619 MJC=0.30013
TF=1.7028E-11 TR=2.7449n ITF=0.0010549 VTF=0.12571\n+ XTF=0.33814 EG=1.11 VCEO=20 ICRATING=20m MFG=SIEMENS)
TEXT -80 232 Left 2 !.tran 1 startup
TEXT -80 264 Left 2 !.options plotwinsize=0
You should really use the measured S-params and use MO/ADS etc.
(simulated together wit the layout). But there are spice models in the
files Infineon files bfr193-spar6ghz-noise1.8ghz-spice-6ghz and bfr181-spar6ghz-noise1.8ghz-spice-6ghz which include the package
parasitics. Listed below to save you searching.
Note that the 181 is a bit of a snowflake in comparison to the 193.
For example as well as the stability the circuit would need to be
checked for startup issues to ensure the vbe limit (only 8V) is not
exceeded. Both of these transistors have the same ft, but apart from
that...
.SUBCKT BFR181 11 22 33
CBEPAR 2 3 7.85E-014
CBCPAR 2 1 4.949E-014
CCEPAR 1 3 1.965E-013
LE 33 30 6.492E-010
LB 22 20 7.342E-010
LC 1 11 6.908E-010
CBEPCK 20 30 1.567E-014
CBCPCK 20 1 1.975E-013
CCEPCK 1 30 1.497E-013
LBI 20 2 6.294E-010
LEI 30 3 7.211E-010
Q1 1 2 3 M_BFR181
.MODEL M_BFR181 NPN( + IS = 9.57E-017 + BF = 131.1 +
NF = 1 + VAF =
71.02 + IKF = 0.09745 +
ISE = 1.618E-015 + NE
= 1.692 + BR =
3.287 + NR = 0.959 +
VAR = 4.081
+ IKR = 0.07617 +
ISC = 5.969E-015 + NC
= 1.974 + RB =
9.72444 + IRB = 3.017E-006 +
RBM = 6.94667
+ RE = 0.7979 +
RC = 2.089
+ XTB = 1.303 +
EG = 1.11 + XTI =
6.548 + CJE = 8.287E-014 +
VJE = 0.8281 + MJE
= 0.7138 + TF =
1.72653E-011 + XTF = 0.07 +
VTF = 0.00381019 + ITF
= 0.027024 + PTF =
0.397851 + CJC = 8.781E-014 +
VJC = 0.7715 + MJC
= 0.7552 + XCJC =
0.6209 + TR = 1.71536E-008
+ CJS = 0 + MJS
= 0
+ VJS = 0.309
+ FC = 0.6275 +
KF = 0 + AF =
1)
***************************************************************
.ENDS BFR181
.SUBCKT BFR193 11 22 33
CBEPAR 2 3 6.251E-013
CBCPAR 2 1 2.028E-013
CCEPAR 1 3 2.08E-013
LEI 3 30 4.62381E-010
LBI 2 20 8.57656E-010
CBEPCK 20 30 1.567E-014
CBCPCK 20 1 1.975E-013
CCEPCK 1 30 1.497E-013
LB 20 22 7.342E-010
LE 30 33 6.492E-010
LC 11 1 6.908E-010
Q1 1 2 3 M_BFR193
.MODEL M_BFR193 NPN( + IS = 8.17971E-016 + BF = 108.285 +
NF = 1.003 + VAF
= 36.5472 + IKF =
0.273876 + ISE = 6.20271E-016
+ NE = 1.553 +
BR = 42.76 + NR
= 0.9775 + VAR =
28.4
+ IKR = 0.01296 +
ISC = 3.44E-015 + NC
= 1.338 + RB =
1.75232 + IRB = 0.0001443 +
RBM = 0.967481
+ RE = 0.310454 +
RC = 0.133617
+ XTB = 1.303 +
EG = 1.11 + XTI =
6.548 + CJE = 2.126E-012 +
VJE = 1.052 + MJE
= 0.47 + TF =
1.58062E-011 + XTF = 0.0395 +
VTF = 0.0696445 + ITF
= 0.00207564 + PTF =
0.0817673 + CJC = 7.142E-013 +
VJC = 0.6315 + MJC
= 0.3991 + XCJC =
0.1208 + TR = 1.58463E-008
+ CJS = 0 + MJS
= 0
+ VJS = 0.75
+ FC = 0.675369 +
KF = 0 + AF =
1)
*************************************************************** .ENDS
BFR193
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself
- just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly.
If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself - just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly.
If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uos4qkdjne2to0cq5e6hc7kd4nr9fbnv5f@4ax.com...
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself - just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly.
If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your
circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo
I wasn't able to download any file from the link you provided.
On Sat, 28 Feb 2026 09:51:16 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uos4qkdjne2to0cq5e6hc7kd4nr9fbnv5f@4ax.com...
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself - just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly.
If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your
circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo >>>
I wasn't able to download any file from the link you provided.
https://mega.nz/file/Ao1xnSya#RGcDsQxLDNUyaZFKP1d3KW55N9RKRT0CsBFTsAA9VxY
On Sat, 28 Feb 2026 09:51:16 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uos4qkdjne2to0cq5e6hc7kd4nr9fbnv5f@4ax.com...
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself - just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly.
If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your
circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo >>>
I wasn't able to download any file from the link you provided.
https://mega.nz/file/Ao1xnSya#RGcDsQxLDNUyaZFKP1d3KW55N9RKRT0CsBFTsAA9VxY
On Sat, 28 Feb 2026 19:56:02 +0000, JM
<sunaecoNoChoppedPork@gmail.com> wrote:
On Sat, 28 Feb 2026 09:51:16 -0500, "Edward Rawde" >><invalid@invalid.invalid> wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:uos4qkdjne2to0cq5e6hc7kd4nr9fbnv5f@4ax.com...
On Fri, 27 Feb 2026 23:26:05 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
Thanks for that. Here is my first 6GHz oscillator.
100 ohms for R4 kills oscillation but 10 ohms is not sufficient.
The ferrite bead with the lowest L in the LTSpice library doesn't kill it but some of the others I tested do.
You're making life hard for yourself - just change the transistor
symbol type to a subcircuit (X) and use the subcircuit model directly. >>>> If you change the subcircuit names to numerics you can also step
through the different transistors - see below where I've changed your
circuit.
(I'll upload to mega instead because the netlist will probably need
manual editing otherwise.)
https://mega.nz/file/05kVyDZY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo >>>>
I wasn't able to download any file from the link you provided.
https://mega.nz/file/Ao1xnSya#RGcDsQxLDNUyaZFKP1d3KW55N9RKRT0CsBFTsAA9VxY
oops, try this
https://mega.nz/file/11kgHRJY#an5rHSPesfthy0fJ9W8Hw9kyD8zmMgebGLbh0nZDBIo
A subckt to schematic converter would be nice but I can understand why that's hard.
On Sat, 28 Feb 2026 20:25:18 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
A subckt to schematic converter would be nice but I can understand why that's hard.
There are netlist browsing tools available, but the free ones are
pretty useless. This link is a view of the BFR193 subcircuit using a commercial tool, to show the type of schematic they generate.
https://mega.nz/file/d5FkmKgA#Gf53z94th9dgzrnmLNbK8ttmE_Tzbhe65cjxC4EGTkE
| Sysop: | Amessyroom |
|---|---|
| Location: | Fayetteville, NC |
| Users: | 59 |
| Nodes: | 6 (0 / 6) |
| Uptime: | 19:28:07 |
| Calls: | 810 |
| Calls today: | 1 |
| Files: | 1,287 |
| D/L today: |
10 files (21,017K bytes) |
| Messages: | 194,198 |