This variable filter that lets frequencies from 500 Hz to 1500 Hz pass through was found in a Popular Electronics from the 90's. The operational amplifiers are the 741.
Originally designed to analyze the shape of light pulses from a flash for photographic...
This CMOS oscillator circuit generates signals up to a few megahertz, depending on the capacitor value....
Generating sinusoidal signals from 1.5 to 15 kHz, this oscillator uses common complementary...