This circuit was found in Radio Electronics from the 90s. The components used are common, and the transistors and CIs must be equipped with heat sinks.
The circuit in the figure is based on an LM101A; diodes can be replaced with equivalents. The...
This circuit, with magnetic sensor, uses an operational amplifier of the time. The circuit is from...
Found in a 90s Popular Electronics, this circuit checks if a remote-control transmitter is...