I am building a Valley People Trans Amp.
It uses paralleled PNP transistors, diff circuit, with a constant current source.
I am trying to figure out the best way to match transistors.
The VP uses closely matched transistors that are thermally coupled, one transistor from the + side of the signal input gets thermally coupled with one from the minus side.
I have used Emitter Base voltage to match them, Collector voltage, etc.
(dc matching)
I am now using a more dynamic matching method, injecting a sawtooth wave form and comparing the two transistors.
Bias and collector resistors have been matched to the nearest ohm.
I am looking at the output voltage on the collectors to match the transistors up.
My problem is that I can get a match at 100 hz, but at 10,000 hz, they no longer match. So what frequency should I use as a standard to match with?
Thanks,
cj
Let me know if youm need a schematic.
It uses paralleled PNP transistors, diff circuit, with a constant current source.
I am trying to figure out the best way to match transistors.
The VP uses closely matched transistors that are thermally coupled, one transistor from the + side of the signal input gets thermally coupled with one from the minus side.
I have used Emitter Base voltage to match them, Collector voltage, etc.
(dc matching)
I am now using a more dynamic matching method, injecting a sawtooth wave form and comparing the two transistors.
Bias and collector resistors have been matched to the nearest ohm.
I am looking at the output voltage on the collectors to match the transistors up.
My problem is that I can get a match at 100 hz, but at 10,000 hz, they no longer match. So what frequency should I use as a standard to match with?
Thanks,
cj
Let me know if youm need a schematic.