This old circuit from a documentation from the 70s disconnects a TV from a signal obtained on the TV itself, detecting when the tuned channel goes out of the air.
This circuit shows how to get 5 V under low current from an operating amplifier 741. I got this...
This circuit uses two JFET such as the BF244 or BF245 and has an excellent gain with small...
This circuit was found in the March 1995 issue of Electronics Now magazine. The circuit requires a...