I'm trying to measure a variable resistance, RX, creating an AC voltage with two PWM and applying it to a wheatstone bridge. The PWM goes from 0 to 3.3v and to measure the voltage differential i'm connecting each arm to a InAmp to read after with a ADC. My problem is that my circuit is unipolar (+3.3v) so i'm looking for solutions to create an negative voltage source (-3.3v) to power the opamp in the negative rail to avoid saturation. I read about charge pumps, is there any other better solution ?
Thank you in Advance.