Found in a1967 Ferranti documentation, this circuit uses an operational amplifier from that time. The circuit uses a LDR as a sensor and has a null setting.
This circuit is from an American publication from 1975 and can use other operational amplifiers and...
This circuit generates audio signals for testing amplifiers and other equipment. The potentiometer R5...
This circuit was found in a 90s EDN. In it we have the use of LEDs and diodes to stabilize the supply...