Amplifier design knack ???

[jan.didden]

Re: sharp thinking

Hi Jan,
I agree with Occam. Makes my eyes water for some reason!

I understand what you are pointing out: that if the output transistors are "off" then the drivers will be driving the load through R36etc, but in my opinion this is not what they are for, as their values are so high that very little current will flow to the load this way. Generally, the output transistors are biased so that they are never both completely off at the same time. I suppose the drivers driving the load directly is more likely to be effective in the CFB configuration.
Just my opinion.
BAM

Yeah, you may have a point there. I'll see if I can uncover those Elektuur diagrams, see what resistor values they used.

Jan Didden

 

[ward]

I think most of can agree that this resistors do have a purpose. Compare all darlingtons and huge "tripletons". Everyone almost have these resistors.

In class A and B, increase linearity and speed

In class D, decrease switch off time.

Those resistors aren't for fun. Semiconductor manufactures don't do anything for fun. It must serve a purpose.

====================================
Thanks everybody's comments !!!

According to Rod Elliots article ,the resistor such as R36/37 not only speed up the turn off time but also improve the thermal stability of output transistor.
and with low value resistor brings output transistor will not turn off especially in high frequence.
Does anybody obvious on this theory ?
and Is it possible to introduce such knack to build class A amplifier that maintaining output stage transistor always on besides without high quiescent current.
Appreciated for your comments again ^.^

ward

 

[capslock]

Another aspect of those resistors was that it was easier to stabilize the bias current through the output devices.