This amplifier was found in a 1957 Rayrtheon documentation. The circuit can be fitted with a BC558 transistor. Driver and output transformers can be obtained from unused transistor radios.
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...