I need to implement the equivalent of a variable resistor of range 10 – 200 Ohms, to be controlled by a microcontroller or FPGA. It is for a gain setting resistor for an op-amp, so I need be ends of the ‘resistor’ available (ie. not one at ground).
What is a cheap, simple way to implement this?
I’m thinking of using analog switches with various resistors, but I can’t think of a structured way to choose these. Maybe this is another question, but if this is the best way to go, then what is a good way to find the setup and values?
Digital potentiometers have too high wiper resistance to use here.