Found in a 1968 American documentation, this circuit uses an operational amplifier that is uncommon today. The feed must be symmetrical. The gain is 40 dB.
This high-gain circuit was found in an American publication from the 1990s. The circuit can use...
This circuit automatically controls the degree of illumination. As the circuit is from 2001, it...
This circuit was found in a Radio Electronics from April 1990. The circuit has 5 equalization...