This simple wireless microphone circuit for the MW band was found in an old American documentation. The coil is the oscillator of an old MW radio.
This circuit was found in a Hands On Electronics from the 90s. The microphone is a small 75-ohm...
This JFET amplifier stage was found in the Encyclopedia of Electronic Circuits Volume 5 from 1995....
To obtain more output power from an operational amplifier, we can use a transistor, as shown in...