The circuit shown is from the 1994 Linear Applications Handbook by National Semiconductor. The base is a transconductance operational amplifier.
This circuit was originally recommended to operate with the emitter of the previous circuit but...
When the probes of this circuit meet water, the relay closes its contacts. The circuit is from a May...
The power supply shown can supply voltages of approximately 0 V to 12 V with a maximum current of 4.5 A,...