Upper Limits of Biasing 2SC2922 2SA1216

[AndrewT]

The glaring omission from this thread so far (unless I have somehow missed it) is the output stage topology. CFP or Darlington? It makes a huge difference to optimum quiescent current. To a first approximation the best current does not vary with BJT type, but it varies greatly with topology and emitter resistor value.

yes the question was asked but never answered some 7 years ago

what output stage is fitted?

Strange - nobody mentioned that earlier,

7 years ago was admittedly a bit too far back to remember.

 

[sajti]

yes the question was asked but never answered some 7 years ago7 years ago was admittedly a bit too far back to remember.

Answered...

PM11 has triple darlington output. There are 0.1ohm emitter resistors. So 10mV means 50mA.
You can increase up to the thermal shutdown...

Sajti

 

[AndrewT]

PM11 has triple darlington output.

That was 2 days ago, not 7years ago.

 

[DF96]

Assuming standard BJTs (e.g. no built-in ballast resistors) then the transistor type does not matter too much. It is the circuit which determines the best quiescent current setting. One ought to be able to assume that the original designer knew what he was doing.

Saying "what is the best bias setting for BJTs 2SCxyz?" is a bit like asking "what is the best engine idle speed when I have Acme XYnn tyres on my car?".

Anyway, as I said, I suspect that for Darlington outputs there is no optimum setting. Or at least, it is a very broad setting so not worth worrying about.