This circuit is from Motorola's 1990 Linear Databook. The transistors allow equivalents and the output power depends on the supply voltage. The power supply must be 30 V symmetrical.
This simulation shows how to use an operational amplifier as a voltage comparator. The sample uses the...
This circuit automatically activates the relay when the phone is answered, closing the record...
This car alarm was found in an American '80s documentation. The circuit automatically activates...