A high-voltage electro-optic driver with DMOS power FETs and optocoupling isolation

A high-voltage, high-frequency linear amplifier/driver for capacitive loads

“…Thus, the total harmonic distortion at full output (3.4 kV) does not exceed 0.04%. This compares very favourably with the figure of 0.5% quoted for an optically isolated amplifier with lower output voltage capability (Theophanous et al 1988) and is qnite o-tstandixg by any s:andards. !t mas:, of caurse, be recognized that the harmonic content increases dramatically if clipping or slew-rate limiting occur.…”

“…Very small variations were observed during warm-up, and it is unlikely that such effects would be significant under laboratory conditions provided high-stability components are used. In this respect, performance is much better than amplifiers utilizing optical isolation, where gain coefficients of order 1 % "C-' have been reported (Theophanous et al 1988).…”

“…Power consumption was also at a premium with a nominal target of 60 W from a 48 V DC Triangular waveform fidelity represents a particularly challenging problem in this application as the predominantly capacitive load of crystal plus connecting leads (around 50 pF was anticipated) requires the amplifier to source and sink a constant current of several mA on alternate half-cycles and, in addition, a wide small-signal bandwidth (of order 1 MHz) is needed if the amplitude and phase relationships of the Fourier components are to be accurately reproduced. Although a number of kilovolt solid state amplifiers have been described in the literature, none appear to combine all of the features required, being either frequency-limited (Skurnik 1986, Krasnov andFomin 1988), excessively nonlinear (Theophanous et al 1988) or otherwise unsuitable on grounds of output voltage or power consumption.…”