An efficient switching amplifier for driving a capacitive load

The development of a high efficiency, high voltage, phase linear amplifier for driving a capacitive load is described. With a load of 35 nanofarads, output signals approaching 200 volts peak-to-peak axe obtained with power dissipation on the order of 25 watts for a 33 KHz, 80 volt amplitude output sine wave. The amplifier has a phase linear characteristic and a -3 dB cutoff frequency of 80 KHz. This allows transmission of wide bandwidth ultrasonic signals whose carrier frequency is in the range of 20 to 40 KHz. The amplifier is of a switching topology to reduce power consumption. The amplifier consists of a pulse width modulator, high frequency switches, and a linear-phase, passive, low pass filter.