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.
This configuration is also valid for other operators and the formula for calculating the gain is...
This inductively coupled oscillator was found in an American documentation from the 90's. The...
This circuit was obtained from an Analog Devices manual from the 90's. The integrated circuit is...