The presented circuit was found in the National Semiconductor FET Databook. The setting applies to other operational amplifiers and other FETs. The power supply must be symmetrical.
In the figure we have a classic Clapp oscillator configuration for a frequency of a few tens of...
This circuit takes advantage of the inductance of the phone in the resonant circuit. The circuit is...
In the figure we have the way to increase the voltage of a 78xx by adding a zener diode. The...