Servo amplifier (T454E)

Found in a MIT publication from the 1940s, this circuit shows use in a servo amplifier. The supply is made with different voltages.

Power Zener (CB216E)
Using in operational amplifier is possible to increase the dissipation power of a zener. This...
1 kHz Tone Recognizer (CB1428E)
This circuit is found in a 1975s documentation for radio amateurs. It was developed to recognize a...
Fluorescent Rhythm Light For the Car (CB3810E)
This 1987 circuit uses a common ignition coil to generate high voltage to power a fluorescent lamp that...