This circuit uses an LED (called SSL) to regulate current in a configuration with complementary transistors. The circuit is from 1970 General Electric documentation.
This low pass filter has attenuation of 5.5 dB and the frequencies depend on the values of the...
This circuit is from an old 80's linear circuit manual. The configuration can be implemented with modern...
Found in an American 1980s documentation, this circuit makes use of a sensor of the era uncommon...