This is a low cost design, of a amplifier with a electret microphone capsule for the ADC of a 3.3V micro-controller. Using the OpAmp LM358P with 3 stages. 1º JFET stage, 2º and 3º OpAmp stages. The ...

We’re talking of course about the carbon microphone amplifier, a piece of telephone technology which made its way into consumer electronics. The carbon microphone is a container of loosely ...