4093 Sine Square Converter (CB26335E)

Found in a Popular Electronics from the 90s, this circuit operates up to about 5 MHz input.

Solar power supply for tunnel diode (CB23827E)
In the figure we have a way of using a solar cell as a source for circuits with tunnel diodes. The solar...
Graphic Equalizer (CB24554E)
This equalizer was found in the May 1978 issue of Radio Electronics magazine. The component values...
Headphone Amplifier (CB21550E)
This circuit for high-impedance magnetic headphones was suggested as an experimental amplifier for hearing...