The AD637 is a complete， high accuracy， rms-to-dc converter that computes the true rms value of any complex waveform. It offers performance that is unprecedented in integrated circuit rms-to-dc converters and comparable to discrete and modular techniques in accuracy， bandwidth， and dynamic range. The AD637 computes the true root mean square， mean square， or absolute value of any complex ac （or ac plus dc） input waveform and gives an equivalent dc output voltage. The true rms value of a waveform is more useful than an average rectified signal because it relates directly to the power of the signal. The rms value of a statistical signal relates to the standard deviation of the signal. Superior crest factor compensation permits measurements of signals with crest factors of up to 10 with less than 1% additional error. The wide bandwidth of the AD637 permits the measurement of signals up to 600 kHz with inputs of 200 mV rms and up to 8 MHz when the input levels are above 1 V rms. Direct dB value of the rms output with a range of 60 dB is available on a separate pin. An externally programmed reference current allows the user to select the 0 dB reference voltage to correspond to any level between 0.1 V and 2.0 V rms. A chip select connection on the AD637 permits the user to decrease the supply current from 2.2 mA to 350 μA during periods when the rms function is not in use. This feature