We found this circuit in the Linear Applications Handbook by National Semiconductor. It uses the LM3900, an operational transconductance amplifier as a base. Q1 can be a 2N2222 or similar.
This circuit for heating elements was taken from a 1966 General Electric manual. The SCRs are...
This circuit also detects leaks and rain. I found it in a 1967 English magazine, but it can be...
August 2017 - This Maxim component, available from Mouser Electronics, is ideal for wearables,...