This circuit is from the Motorola Linear Databook of 1990 and can be implemented with other operational amplifiers. The power supply must be symmetrical.
This simple electroscope with bipolar transistors is not the most sensitive, but can detect static...
This circuit is suggested by Texas Instruments in his Optoelectronics Sourcebook. Any photo...
The frequency generated by this circuit depends on the crystal used. Frequencies up to a few tens...