This circuit was found in an English magazine from 1977. Signal inputs and outputs must be shielded, and the circuit can be powered by battery, since its consumption is low.
Two operational amplifiers are used in this source obtained in an American documentation...
This class B push-pull amplifier circuit with a few hundred milliwatts of power was found in an...
This circuit is from the Motorola Linear Databook of 1990. The coils must be according to the...