The gain of this amplifier is given by the components indicated in the formulas next to the diagram. The power supply must be symmetrical and equivalent operational amplifiers can be used.
I found this circuit in a 1986 English magazine. It can still be easily assembled, replacing the...
This circuit was obtained in a Motorola manual from 1978. We can use any triac and the coupler with...
This circuit, from an old publication, can employ silicon transistors like the BC548 and the...