Any high-gain Darlington transistor can be used on this touch circuit. The load can be formed by LEDs and the power supply isolated from the power grid.
Found in a European magazine from the 1980s, this circuit can amplify signals from 10 kHz up to...
The circuit in the figure uses the four current amplifiers of the LM3900 to generate a sawtooth signal...
This circuit is from a Radio Electronics magazine from August 1960. It is a commercial circuit for marine...