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.
We found this circuit in 2005 Linear Technology documentation. The integrated circuit is LT1787...
This circuit counts from 1 to 10 or 0 to 9 using as indicators common LEDs. The circuit can be...
We found this circuit in a Popular Electronics of the 90s. The circuit still uses light bulbs, but...