Using a micro speaker as an active microphone

    Micro speaker converted into active microphone1

Electret microphones are sometimes needed in audio electronics production , which have a high sensitivity. However, a very sensitive microphone can be made with an ordinary micro speaker and a few components.

    The circuit diagram is as above. The circuit will work on a 3V to 9V power supply . An NPN transistor and resistors and capacitors form a common base amplifier , so that low impedance speakers can be used. The gain generated by the circuit exceeds 100.

    Micro speaker converted into active microphone 2

    This circuit will make a regular micro speaker into a very sensitive microphone. The circuit will operate on a 6V to 12V power supply.