Found in a 90s Radio Electronics, this circuit uses a ceramic capacitor (C1) as a sensor. The operational amplifier is a double 741 of the time.
We found this circuit in an old American documentation. Transistors can be modern equivalents. ...
In the figure we have the conventional configuration of a differential amplifier with the...
This 8 A high output power amplifier uses two National Instruments LM12s. The maximum capacity of the...