This low frequency oscillator circuit was found in an Electronic Design from the 90s. The transistors are common types, and the frequency is given by the crystal.
This stethoscope or hearing aid amplifier has excellent gain. It was found in Popular Electronics from...
Found in Fairchild documentation from the 90s, this circuit generates signals with the...
This configuration, widely used in our articles and on this website, uses a 555 to control a relay...