Abstract: A sampled data, analog computing method and circuit for producing an output voltage V.sub.OUT with a magnitude proportional to the root-mean-square value V.sub.RMS of a monopolar input voltage V.sub.DC, first demodulates or chops a time-varying monopolar input voltage V.sub.DC of interest to produce a demodulated or chopped voltage V.sub.CHOP, and then filters the chopped voltage V.sub.CHOP to produce an output voltage V.sub.OUT. The chopping operation is conducted at a duty ratio or modulation ratio proportional to the ratio of the monopolar input voltage V.sub.DC to the output voltage V.sub.OUT, with the result that the magnitude of the output voltage V.sub.OUT is proportional to the root-mean-square value V.sub.RMS of the monopolar input voltage V.sub.DC. The illustrated embodiment of the invention (i) rectifies a time-varying bipolar input voltage V.sub.AC of interest with a precision fullwave rectifier to produce the monopolar input voltage V.sub.