I'm playing around with spice and trying to choose a small-signal transistor to use for an amp project.
Right now i am using the common 2N5551/2N5401. Which I like becouse of the high voltage tolerances.
But it would be nice with some transistors with higher beta, anybody that can give me some tips? preferably some were spice models are available.
I've looked at BC107/BC177 which looks sweet to me, but they have a breakdown voltage of 40-50V. And i was thinking of using +-63V supplies so i am not sure I could use these.
I suspect that this have been up for consideration before but I cant find any good threads.
Thanks
Icko
Right now i am using the common 2N5551/2N5401. Which I like becouse of the high voltage tolerances.
But it would be nice with some transistors with higher beta, anybody that can give me some tips? preferably some were spice models are available.
I've looked at BC107/BC177 which looks sweet to me, but they have a breakdown voltage of 40-50V. And i was thinking of using +-63V supplies so i am not sure I could use these.
I suspect that this have been up for consideration before but I cant find any good threads.
Thanks
Icko
actually i haven't simulated the diff amp yet. mostly i was thinking around it since i saw the datasheet on the 2N5551, 2N5401.
I'm guessing that VCEQ is less than 40V for the transistors, but
i should probably simulate first and ask questions later...=)
Anyway i found 2SC2240 and 2SA970 which seem good enough for me.
but no spice model for the toshiba 2SA970. After googling it seems as there is none from toshiba only zetex.
I'm guessing that VCEQ is less than 40V for the transistors, but
i should probably simulate first and ask questions later...=)
Anyway i found 2SC2240 and 2SA970 which seem good enough for me.
but no spice model for the toshiba 2SA970. After googling it seems as there is none from toshiba only zetex.
.MODEL 2SA970 PNP(Is=465.4f Xti=3 Eg=1.11 Vaf=57 Bf=407.6
+ Ise=4.683p Ne=2.051 Ikf=.3998 Nk=1.192 Xtb=1.5 Var=100 Br=1
+ Isc=465.4f Nc=1.048 Ikr=6.032 Rc=2.343 Cjc=11.59p Mjc=.4014
+ Vjc=1.155 Fc=.5 Cje=5p Mje=.3333 Vje=.75 Tr=10n Tf=1.252n
+ Itf=1 Xtf=0 Vtf=10)
.MODEL 2SC2240 NPN(Is=99.13f Xti=3 Eg=1.11 Vaf=422.2 Bf=352.8
+ Ise=1.179p Ne=1.782 Ikf=.4704 Nk=.9631 Xtb=1.5 Var=100 Br=1.663
+ Isc=555.1p Nc=1.796 Ikr=5.85 Rc=.2032 Cjc=7.561p Mjc=.2472
+ Vjc=.3905 Fc=.5 Cje=5p Mje=.3333 Vje=.75 Tr=10n Tf=1.295n
+ Itf=1 Xtf=0 Vtf=10)
Cascoding
Hello.
Here is a model for the 2SA970.
.model Q2sa970 PNP(Is=465.4f Xti=3 Eg=1.11 Vaf=57 Bf=407.6 Ise=4.683p Ne=2.051 Ikf=.3998 Nk=1.192 Xtb=1.5 Var=100 Br=1 Isc=465.4f Nc=1.048 Ikr=6.032 Rc=2.343 Cjc=11.59p Mjc=.4014 Vjc=1.155 Fc=.5 Cje=5p Mje=.3333 Vje=.75 Tr=10n Tf=1.252n Itf=1 Xtf=0 Vtf=10)
When you put it in your program, make sure to eliminate all returns so it is all one line.
You can (almost) always cascode in order to use a lower voltage transistor so you have the benefits of high gain. Cascoding also increases linearity in some places because it causes C-B voltage to be constant.
There is an example attached.
The MPSA18 is a good high-gain transistor and is often used in LTPs, but I doubt there is a good PNP compliment.
Going by the models, I would say the BCxxx transistors are the most well-matched, but in real life I don't know.
If you are interested but don't know how to implement it in your circuit, give us a schematic and we can help you.
But if you are a beginner I would recommend you start with a simple design.
- keantoken
Hello.
Here is a model for the 2SA970.
.model Q2sa970 PNP(Is=465.4f Xti=3 Eg=1.11 Vaf=57 Bf=407.6 Ise=4.683p Ne=2.051 Ikf=.3998 Nk=1.192 Xtb=1.5 Var=100 Br=1 Isc=465.4f Nc=1.048 Ikr=6.032 Rc=2.343 Cjc=11.59p Mjc=.4014 Vjc=1.155 Fc=.5 Cje=5p Mje=.3333 Vje=.75 Tr=10n Tf=1.252n Itf=1 Xtf=0 Vtf=10)
When you put it in your program, make sure to eliminate all returns so it is all one line.
You can (almost) always cascode in order to use a lower voltage transistor so you have the benefits of high gain. Cascoding also increases linearity in some places because it causes C-B voltage to be constant.
There is an example attached.
The MPSA18 is a good high-gain transistor and is often used in LTPs, but I doubt there is a good PNP compliment.
Going by the models, I would say the BCxxx transistors are the most well-matched, but in real life I don't know.
If you are interested but don't know how to implement it in your circuit, give us a schematic and we can help you.
But if you are a beginner I would recommend you start with a simple design.
- keantoken
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