microphone amplifier circuit

[AlexVRN36]

у

 

[Deleted member 157]

I am not familiar with the transistor types. What are they?

Cheers

Ian

 

[AlexVRN36]

bipolar PNP,germanium planar n-p-n structures

 

[Deleted member 157]

bipolar PNP,germanium planar n-p-n structures

That does not tell me much. What hfe and voltage rating are they?

Cheers

Ian

 

[Mr CMRR]

Since the input stage is operating at something less than 500 µA collector current in this standard x10 (20 dB) gain stage, I'd use a silicon PNP like a 2N4250 for lowest noise. The NPN could be anything general purpose like a 2N3904. Since this stage requires a pull-up to supply voltage on its output, it looks like something to replace electret mics with a dynamic. I'd guess it runs on 9 to 15 V through a load resistor to give a few mA to the output transistor. What is the issue with it?