A precision power amplifier for power/energy calibration applications

A precision power amplifier for use in power/energy calibration applications is described. The amplifier was primarily designed to boost the output amplitude of a digital generator to provide the nominal 120- or 240-rms voltage component of a "phantom" calibration power source. The amplifier has a fixed gain of 40 and can provide a maximum output voltage swing of 970 V peak-to-peak or 340-V rms at 100-mA rms. The bandwidth is from dc to 150 kHz and at 60 Hz the observed no-load short-term amplitude and phase instabilities are ±5 ppm and ±5 μrad, respectively. The amplifier design uses high-voltage N-channel MOSFET's in the output driver stage together with a unique circuit topology of opto-isolators between the low-level input stage and the high-level output stage.