Im building a dual-slope ADC for a university project which needs to run on +12V and 0V supply. Vin can range from 100 uV to 2 V. I have read up about the integrator circuit and think I know how it works. Using the Vout = 1/RC|Vin.dt formula have calculated the RC values. I have a couple of problems though: How do I create the negative Vref voltage with only 0 and 12V? Charge pump type circuit? or maybe bias the voltage regulator? How do you determine what size R and C should be? eg 1uF & 22k or 1nF & 220k ect does it even matter? How do I build the digital switch shown in the diagram? Multiplexer from a few FETs?