Current to frequency solution-High accuracy

Hi Yunjing,

It is not trivial to measure ~0 current, let alone with high accuracy. The input probably needs to be treated differently as two or more regions, you may want to define the lowest current for this reason. Another factor is the voltage imposed by the current source, it will influence the topology and component selection.

In any case, here are a couple of designs. Neither accomplishes this task directly without modification, but they should offer valuable guidance and serve as a good starting point.

Design 1, with current sense amplifier;

Design 2, with operational amplifier or instrumentation amplifier.

Regards, Guang