# Microphone Capacitor Value

I want to use a CMC-5042PF-AC microphone (datasheet: http://www.cui.com/product/resource/digikeypdf/cmc-5042pf-ac.pdf) to send the type of audio signal a component would expect on an RCA line (line level I am guessing). It's going to go to a wireless video/audio transmitter, which would normally except a line level signal form an audio source such as a security camera.

Here is the schematic for the mic:

I am connecting it to 5V power. From what I understand, the R1 resistor would determine the sound level, so I can play around with that to figure out what works best. But what about the capacitor? I can't find in the datasheet what kind of capacitor to use. I have seen people in other schematics use a 1uF cap. Is that what I should do? Or is there a formula I need to use to figure out the cap I need. Also, does it matter if it's a ceramic cap?

Thanks for any hints.

• It's just the normal RC frequency formula. May 3, 2016 at 4:03
• The datasheet suggests values. Look right under the circuit diagram. May 4, 2020 at 21:25

R1 (RL in your circuit) determines the microphone gain and the output impedance of the microphone. Basically the output impedance is RL. If RL is (say) 2k2 then the amplifier that C connects ought to have an input impedance (resistance) => 22k. If it is 22k then C and the 22k form a high pass filter limiting the low frequencies and, at a frequency of $\dfrac{1}{2\pi RC}$, lower frequencies progressively attenuate more and more.