I'm working on a circuit that can act as a current sink or source. The goal is to control it using some digital means so it can output the required current. Right now I am not sure about the implementation of the resistor control, perhaps someone has a suggestion? The circuit has to be very accurate and stable.
The output is set by adjusting R2. If R1 = R2 the output will be 1mA (I1), if R1 = 2 x R2 the output will be 2mA (2 x I1). If the current is fed sourcing, this will act as a current source. If the current is fed sinking (reverse current source polarity) this will act as a current sink.
The design requires stable current source / sink. The design requires very low input bias current op-amp - something that costs $15+ and can be obtained easily The design calls for very accurate resistors as the relations between them sets the output. I would like to put 2 or 3 resistors with relays instead of R2 and switch between them.
What do you think about a digital potentiometer?