Supplement to a comment
Recently I read some articles of a terrific guy (N6QW). Among many other circuits that I have found on his blog is a mic amplifier using PNP (and not NPN) transistor. Firstly I simulated it by using a NPN transistor and after that by using the exact transistor of the original schematic. The related posts are http://n6qw.blogspot.gr/2016/09/40m-junk-box-ssb-transceiver-microphone.html and http://n6qw.blogspot.gr/2016/09/taking-break.html. I posted a comment in the article of the 2nd link and here I post some screenshots related to my comment.
I made a rearrangement of R1, R6+C5 and C4. Although there is no difference in the operation of the circuit, for perception and uniformity purposes perhaps it would be better if in the drawing the R1, R6+C5 and C4 were directly in parallel. As far as audio frequencies is concerned there is no difference (voltage source V1 acts as a short circuit at audio frequencies).
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| From http://n6qw.blogspot.gr/2016/09/40m-junk-box-ssb-transceiver-microphone.html |
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| N6QW's schematic with a rearrangement of R1, R6+C5 and C4 |
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| Using NPN transistor |
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| Both circuits, parameterization of Rser |
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| Addition of Rload |
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| Effect of Rload on the output level and on the frequency response |
