This 1965 circuit uses a Philips 4068 tube to measure extremely small charges. The circuit has as indicator a micro ammeter and the transistors are of the time.
Audio signals can be produced by this circuit. Frequency range is determined by C1 and adjusted by...
This Colpitts crystal oscillator was found in an American publication for amateurs in the 1980s....
This configuration presents a negative resistance caracteristic such as the one found in...