We found this circuit in a 1966 US documentation. It simulates a variable capacitor that can vary capacitance from 1,000 to 1. Transistors are general purpose types.
In the figure we have a wireless wiretapping circuit for the frequency range determined by L1. For FM...
This voltage follower or amplifier with unit gain uses an unusual operational amplifier nowadays. The...
Found in a 90’s Electronics Now, this circuit has its output connected to an audio amplifier. The...