I am in the middle of an impasse in my way to a design with my newborn knowledge on CANbus and decided trying to complete the design of a VCA for a function generator, pending for more than 6 months.

Accepting that I will reinvent the wheel, my questions:

a) From this two transistors, which should be the best for using, previously matched?

2N3904 NPN low signal hFE 40 to 300
BC337 NPN audio hFE 100 to 360

Both are really cheap so cost is not a point here.

b) Given stable / same conditions for the testing of the transistors, should I look for just same Vbe or should I look for same hFE? Measuring Vbe is much easier and faster in a breadboard. Did some practice today.

I've read a lot in the Web but found too much blah blah on the subject.

Comments on the whole subject, welcome.

OTA's are not an option, at least for the moment.

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Agustín Tomás
In theory, there is no difference between theory and practice. In practice, however, there is.

 

I answered you half an hour ago on another website.

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Uncle $crooge

 

You can buy ICs that contain matched transistors.

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I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

Are ICs still available with matched transistors for people who make their own opamps?

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Uncle $crooge

 

National still make them.
http://www.national.com/mpf/LM/LM394.html
http://www.national.com/mpf/LM/LM3046.html

__________________

I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

I remember the old CA3046, MC3046 and LM3046.

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Uncle $crooge