I need to amplify an electret microphone for use with an Arduino Uno. I have a few capacitors and resistors and several transistors one of which is an N-channel. Any ideas? Can you please also provide me with a scheme?

  • 1
    \$\begingroup\$ I don't understand. We cannot use resistors, capacitors, other transistors, or ICs? \$\endgroup\$
    – Telaclavo
    Commented Apr 25, 2012 at 15:16
  • \$\begingroup\$ We also have resistors 10 kiloOhms and 220 Ohms \$\endgroup\$ Commented Apr 25, 2012 at 15:18
  • \$\begingroup\$ The Arduino Uno isn't a PIC! Question cannot be answered and should be closed. \$\endgroup\$ Commented Apr 25, 2012 at 15:18
  • 4
    \$\begingroup\$ @LeonHeller: it seems that more and more people think PIC is another word for microcontroller. "The PIC is an Atmel AVR." \$\endgroup\$ Commented Apr 25, 2012 at 15:21
  • 2
    \$\begingroup\$ This is most easily done with a opamp. It's not too hard to do it with a few transistors either, but some other components like a few resistors and capacitors will be needed either way. Restricting the problem to what you happen to have on hand is silly because it's easy to get these other parts. \$\endgroup\$ Commented Apr 25, 2012 at 15:21

1 Answer 1


Ok this will be quick and hopefully painless.

microphone amplifier

I am not well versed in the microphones themselves, sometimes they are biased sometimes they are not.

So the way this is designed:

Remove DC bias from microphone output

Bias the transistor so that it can maximize the usable range

(For simplicity make R1= R2 10k resistors or less should do it)

Rg (plus the beta of the amplifier) control the gain of the circuit. The higher Rg the higher the gain. HOWEVER, the larger Rg gets the more power it dissipates. this is for low current systems.

the transistor is an NPN (always open, apply voltage to close)

This is also an INVERTING amplifier. For audio applications you will not hear the difference; however, if you use it for anything else it applies a negative gain.

(Vout= -Gain*vin)

  • 2
    \$\begingroup\$ That transistor looks like an IGBT... \$\endgroup\$
    – stevenvh
    Commented Apr 27, 2012 at 6:13
  • \$\begingroup\$ you can use almost any transistor, but if you want the signal to remain linear with minimal harmonic distortion, i advise using an npn. \$\endgroup\$
    – CyberMen
    Commented Apr 27, 2012 at 12:52
  • 1
    \$\begingroup\$ Yes, I already guessed it's supposed to be an NPN. You definitely don't want an IGBT for this! :-) \$\endgroup\$
    – stevenvh
    Commented Apr 27, 2012 at 12:54
  • \$\begingroup\$ also i wrote above it was an NPN >_<; \$\endgroup\$
    – CyberMen
    Commented Apr 27, 2012 at 12:55
  • 2
    \$\begingroup\$ No problem, I only meant to say that the symbol you drew looks like having an insulated gate. \$\endgroup\$
    – stevenvh
    Commented Apr 27, 2012 at 12:58

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.