The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. The base is a transconductance operational amplifier.
Found in an Electronic Design from the 80's, this circuit monitors a three-phase line, activating a...
Relays from 20 mA to 200 mA can be driven by this sensitive circuit.6 or 12 V relays can be used...
All the components used in this 1997 circuit are still common in our market. The circuit must be...