PC resistance meter (CB20544E)

We found this circuit in English documentation for PCs from 1996. The ZN448 is a very uncommon integrated circuit today. It is an interface circuit.

Directed Coupled Two Transistor Stage (CB972E)
This circuit was found in an old documentation from 1968. The voltage gain is 70 and the...
High Q Notch Filter (CB4834E)
This notch filter or reject filter rejects signals of a certain frequency with good selectivity. The...
Power Supply with Operational Amplifier 12 V x 500 m (CB1171E)
This circuit was found on a Radio Electronics of July 1984. It consists of a source with the 741...