Two transistors on a regenerative switch are used to trigger a triac. This circuit is from the RCA Power Circuits manual. Transistors admit equivalents.
In figures 1 and 2 we have two current drains that can be made with operational amplifiers and...
Great sensitivity for the circuit can be obtained with a Darlington amplification step for the...
The used diode is an unusual component today. We found this 12 V regulator in documentation from the...