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 is from a publication from the 50's. Inductive components are critical, and...
This simple two-transistor circuit used transistors from the 60s, having been found in a...
This circuit uses an oscillator that generates a signal of approximately 1450 kHz to test...