This circuit was obtained in the 1990 Motorola Linear Databook. The circuit uses a 139 series comparator, but other series can be used. The power source need not be symmetric.
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...