pmos+nmos to form 1:2 muxes (i.e. single-pole double-throw switches) for capacitor stacking...pmos gate must be -1.2v lower than source voltage

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sim

can have a comparator for each bit that updates that bit's switch according to whether is bigger or smaller than the analog input voltage. Then higher bits will follow like dominoes, for really fast ADC conversion. The DAC conversion could also be really fast by simply writing the digital number as parallel output from a microcontroller or FPGA. Or could go through a SIPO shift register. Could also of course shift ADC conversion bits into the microcontroller too.

Can start conversion with all bits low, producing 0v at top of stack. Can fix comparator + input to top of stack and - input to analog input signal. Then toggle first bit high. If comparator output is high, then leave that bit set high, else turn that bit off. Continue up the ladder, testing and updating each bit sequentially.