This circuit was obtained in an Electronic Design from the 80's. It has the adjustment of the gain through a simple potentiometer. The power supply must be symmetrical.
This amplifier was found in a Japanese publication in 1972. Transistors are uncommon today, and...
The current of this source is 200 mA at the most, and the output depends on the zener that may...
Found in Mallory documentation from 1968 this circuit uses an integrated circuit from that time. The...