High gain radio (CB21922E)

This simple 1 transistor radio was found in Raytheon's transistor manual. The transistor is germanium from the 60s.

Tunnel Diode Voltage Regulator (CB12876E)
This circuit from an old Argentine publication shows how it is possible to use a tunnel diode in a...
Breakout board for DC motor reversal (CB23714E)
To invert the rotation of a motor by changing the levels of an Arduino output or another...
50mA driver (CB20924E)
This ultra-low distortion driver was found in 80's Analog Devices documentation. The circuit has a...