The AD536A is a complete monolithic integrated circuit that performs true rms-to-dc conversion. It offers performance comparable or superior to that of hybrid or modular units costing much more. The AD536A directly computes the true rms value of any complex input waveform containing ac and dc components. A crest factor compensation scheme allows measurements with 1% error at crest factors up to 7. The wide bandwidth of the device extends the measurement capability to 300 kHz with less than 3 dB errors for signal levels greater than 100 mV. An important feature of the AD536A, not previously available in rms converters, is an auxiliary dB output pin. The logarithm of the rms output signal is brought out to a separate pin to allow the dB conversion, with a useful dynamic range of 60 dB. Using an externally supplied reference current, the 0 dB level can be conveniently set to correspond to any input level from 0.1 V to 2 V rms. The AD536A is laser trimmed to minimize input and output offset voltage, to optimize positive and negative waveform symmetry (dc reversal error), and to provide full-scale accuracy at 7 V rms. As a result, no external trims are required to achieve the rated unit accuracy
