The circuit shown is from 1994 National Semiconductor documentation but can be implemented with more modern operational amplifiers. The power supply must be symmetrical.
We found this circuit in an old American documentation. SCRs can be modern equivalent types. The...
We found this circuit in a 1990 documentation. The operational amplifiers are type 741 and the LED is...
This fast-acting circuit uses a 555. We found it in the November 1992 Radio Electronics magazine. The...