For fun I'm trying to design an epic amplifier with programmable gains from ~1.4 to 256. The opamp being used is a TLV2452.
The digipot A can reach a minimum of 390 Ω. The digipot B can reach a maximum of 100 kΩ.
The voltage source, 3.3 V in the picture, can actually reach much lower values as it's from a real world signal.
The problem that I'm having is that digipot B doesn't seem to work properly. Even when I remove digipot A and replace it with a static resistor, digipot B still shows weird values. It shows negative resistance values over the terminal even when no 3.3 V signal is applied.
I'm confused about how to set the wiper terminals to their correct pins in order for current to flow across them properly. I know the signals that I send to them are working properly because when I isolate each device, the microcontroller changes the resistances correctly. It's only when they get integrated with the opamp - specifically as the forward resistor (like digipot B) that they start to act weird.
For example when the input signal is 1 volt and the gain is at max (256) the opamp will only output 6 V, even when the signal is within the sampling range of my oscilloscope.
Is it possible to use two digital potentiometers in this way?