The Analog Devices AD637SD is a high-accuracy RMS to DC converter IC. It computes the true RMS value of complex waveforms with a 0.02% maximum nonlinearity and 8 MHz bandwidth.
The AD637JD is a high-accuracy, wideband RMS-to-DC converter from Analog Devices. It computes the true RMS value of complex waveforms with excellent linearity and bandwidth.