This circuit from the 1980s uses an operational amplifier that is uncommon today. The circuit can be designed with modern operators. The gain is 40 dB.
This circuit, which can act as a shield, was found in an American documentation from the 90s. The...
This circuit was found in a 1964 Electronic Design. The transistor may be a current equivalent of...
Suggested by Sprague in the 1980s documentation, this circuit can control three-phase AC motors....