In the figure we have the basic configuration of an operational amplifier for audio signals. The circuit is from a Radio Electronics from the 90s. The power supply must be symmetrical.
The circuit shown is suggested by National Semiconductor's Linear Applications Handbook. The base...
This circuit uses a pickup coil to take the signal from a telephone line without contacts. The circuit...
In this circuit, the transistors are NPN for general use and the phototransistors can be replaced by...