Found in a 1960s documentation, this circuit uses an operational amplifier from the time and a current diode, both of which are difficult to find today.
This circuit detects light variations using two LDRs as sensors. Operational amplifiers and...
The circuit shown consists of a power stage for relay excitation. 2N3053 can be a BD135 and 2N406...
This circuit was found in Mullard's 1960s transistor manual. The circuit uses germanium...