Ask a question about Pass AM

[jacksl520s]

Friends, I want to ask a question about the pass am circuit.

The resistance of R8 (1.5k) in the figure. What will be affected by adjusting its resistance value?

Because I see some circuit diagrams, for example, the resistance of pass A3 is 1K

 

[Nelson Pass]

It's a nominal value, but increasing it will increase the bias a bit depending on the current gain (beta) of Q3.

 

[jacksl520s]

It's a nominal value, but increasing it will increase the bias a bit depending on the current gain (beta) of Q3.

Thank you for your reply

Whether changing it will affect the current of the constant current source

 

[Nelson Pass]

It will have small effect. The main effect is the .7v base emitter junction voltage.

 

[jacksl520s]

It will have small effect. The main effect is the .7v base emitter junction voltage.

I see. Thank you for your reply!