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.
The operational amplifier is old. The circuit is from an 80's documentation but can be designed...
The connection of high-value input resistors causes the circuit to behave like a conventional...
We find this encoding circuit in an American 1980s amateur radio documentation. The circuit can be...