The AD636 is a low power monolithic IC that performs true rms-to-dc conversion on low level signals. It offers performance that is comparable or superior to that of hybrid and modular converters costing much more. The AD636 is specified for a signal range of 0 mV to 200 mV rms. Crest factors up to 6 can be accommodated with less than 0.5% additional error， allowing accurate measurement of complex input waveforms. The low power supply current requirement of the AD636， typically 800 μA， is ideal for battery-powered portable instruments. It operates from a wide range of dual and single power supplies， from ±2.5 V to ±16.5 V or from +5 V to +24 V. The input and output terminals are fully protected; the input signal can exceed the power supply with no damage to the device （allowing the presence of input signals in the absence of supply voltage）， and the output buffer amplifier is short-circuit protected. The AD636 includes an auxiliary dB output derived from an internal circuit point that represents the logarithm of the rms output. The 0 dB reference level is set by an externally supplied current and can be selected to correspond to any input level from 0 dBm （774.6 mV） to ?20 dBm （77.46 mV）。 Frequency response ranges from 1.2 MHz at 0 dBm to greater than 10 kHz at ?50 dBm. The AD636 is easy to use. The device is factory-trimmed at the wafer level for input and output offset， positive and negative waveform symmetry （dc reversal error）， and full-scale accuracy at 200 mV rms. Therefore， no external trims are required to achieve full-rated accuracy.