This circuit is from an old documentation, making use of an operational of the time. The circuit can be adapted to use modern components. The power supply must be symmetrical.
We found this voltage multiplier circuit in a Radio Electronics magazine from December 1991. The...
The figure shows how to use a CMOS amplifier as a crystal-controlled oscillator. The circuit is...
This simple circuit does not use active components and uses a small speaker as a microphone. The...