Level-shifting nixes need for dual power supply

摘要

The AD736 TRUE-RMS-TO-DC convert-er is useful for many applications that require precise calculation of the rms value of a waveform. This converter can determine the true rms value, the average rectified value, or the absolute value of a myriad input waveforms. Basically, all applications require both a positive and a negative power supply. According to the data sheet, you can use the device with a single supply by ac-coupling the input signal and biasing the common pin above ground. However, the ability to process only ac signals is a major performance limitation. You can lift this limitation by using a level-shifting approach (Figure 1). This approach requires more circuitry, but it removes the ac-only input-waveform restriction.