Found in an Electronic Design from the 90s, this sophisticated continuity tester uses operational amplifiers from that time.
This circuit is from an English publication from 1978, but it can be assembled with BC548 for TR2...
In the figure we have the way to use a voltage comparator powered by a voltage to control a...
This circuit found in a 1993 Electronics Hobbyst Handbook has a very simple configuration that can be used on...