I got a schematic diagram of Electret Condense Microphone(ECM), shown as in the below. I would like to know the function purpose of C1 and C2. Each of value is 33PF and 10PF. Thanks.

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    \$\begingroup\$ My first guess would be the capacitors provide some frequency-selective compensation for the frequency responses of the microphone's mechanics (e.g., the electret diaphragm) or its JFET or both. My second guess is the caps provide additional noise suppression for short-duration impulse voltages on the power supply Vs or ground rails (e.g., switched-mode power supply noise). \$\endgroup\$ – Jim Fischer Nov 22 '17 at 8:09

Electret maker PUI says: "Each microphone features GSM buzz-blocking capacitors," but they work to eliminate other interference as well.

  • \$\begingroup\$ That jives with my guess. 33pf would only help at radio frequencies, so they keep out RF when it's used on a phone. No effect at audio frequencies. \$\endgroup\$ – gbarry Sep 30 '18 at 4:08

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