5 LED Log Scale with U257B (CB25442E)

The circuit was found in the February 1992 Radio Electronics magazine. The scale can be changed by changing R2 and R3.

RIAA preamplifier (CB8250E)
This circuit was obtained in an Electronics World of 1968. The operational amplifiers ones are...
Light Sensor 2 (CB5974E)
This circuit works in the opposite form to the previous one and drives a relay as a load. The...
Active Bandpass Filter (CB6723E)
Found in a 1970 American publication, this circuit uses transistors of the time. These transistors...