This variable filter circuit was found in July 1975 Radio Electronics magazine. The circuit uses 3 general purpose op-amps like the 741 and must use a symmetrical source.
This circuit converts BCD inputs to analog voltages. The operational amplifier must be powered...
This circuit is suitable for the calibration of old analog oscilloscopes. It was found in...
This is the circuit of a hearing aid amplifier manufactured by Sony in the 1960s. The circuit was...