This 4-tube circuit was found in an American publication from 1947. It is intended for audio distribution lines using a transformer source.
Any high-gain Darlington transistor can be used on this touch circuit. The load can be formed by...
This circuit is from an April 1991 Radio Electronics magazine. The circuit uses power MOSFETs and...
We found this circuit in a 1980s Linear Technology documentation. The components are from the...