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 a 1967 Experimenters Handbook. The circuit can be implemented with other...
This circuit is from an old documentation but can be implemented with a BD136 for Q1 and 2N3055 for...
In the figure we have the basic configuration of an inverter transconductance amplifier, as...