High-precision nanoamp level current generator circuit diagram

In practical applications, many special measurement circuits require nanoampere-level high-precision current as a benchmark, and it is difficult to produce them in amateur situations. This article introduces a high-precision nanoamp level current generator circuit for enthusiasts to make their own, as shown in the figure.

This circuit is a microcurrent constant current source. In order to enable the current value to be continuously changed at will, a multi-turn (10-turn) potentiometer is used as a voltage divider to divide the reference voltage, and the current value can be read directly. Then through the current shifting resistors R3 and R4, a wide range of tiny currents can be generated.

The VT tube in the circuit uses a MOSFET tube with very small gate current. The reference voltage is 1V. Adjust the potentiometer RP1 so that RP2 generates a +1V voltage when the current is adjusted to the maximum. RP3 is used for offset adjustment and also improves the fixing accuracy of RP2.