The AD636 is a low power monolithic IC which performs true rms-to-dc conversion on low level signals. It offers performance which 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 A, allows it to be used in battery-powered portable instruments. A wide range of power supplies can be used, from 2.5 V to 16.5 V or a single +5 V to +24 V supply. 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. This signal is derived from an internal circuit point which represents the logarithm of the rms output. The 0 dB reference level is set by an externally supplied current and can be selected by the user 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 a 0 dBm level to over 10 kHz at 50 dBm. The AD636 is designed for ease of use. The device is factorytrimmed at the wafer level for input and output offset, positive and negative waveform symmetry (dc reversal error), and fullscale accuracy at 200 mV rms. Thus no external trims are required to achieve full-rated accuracy. AD636 is available in two accuracy grades; the AD636J total error of 0.5 mV 0.06% of reading, and the AD636K