This circuit is from a Radio Electronics magazine from August 1974. It used one of the first photomultiplier tubes that was to be powered by high voltage. The power came from the mains.
This commercial NEC radio circuit from Japan has an audio power of 300mW and uses 7 germanium...
We found this amplifier for automotive use in the Philips integrated circuit manual from 1990. The...
We find this circuit in a 1980s documentation for amateur radio. The circuit shows how to switch...