This circuit was obtained in a Hobbyst Handbook from 1990. The circuit can be easily assembled since the SCR can be a TIC106 and the transistor a 2N30555.
This circuit is from a Motorola integrated circuit manual. The integrated used is no longer common...
Found in a 1968 US publication, this circuit is designed to measure very weak signals. The...
This circuit was found in the Intersil Databook. The integrated circuit used is uncommon today. R2 sets...