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 appeared in the July 1969 issue of Radio Electronics magazine. The sensor is an LDR....
This circuit was found in an American 80's documentation. The transistor is of germanium of the...
This old 4-channel circuit was found in the December 1994 Electronics Now magazine. The circuit uses...