High-Voltage Amplifier Circuits
by Dennis L. Feucht
Innovatia Laboratories
Some linear amplifiers require an output voltage range that is large relative to the rest of the system. Some applications are: Power pulse amplifiers, motor drivers, piezoelectric transducer drivers, oscilloscope deflection-plate drivers, on-chip programming supplies, analog computers, EL panel and display supplies, and audio power amplifiers. Whether it is 12 V or 1.2 kV, special considerations arise when transistor breakdown voltage becomes a critical design parameter. This article presents circuit alternatives for high-voltage (HV) amplifiers, and their relative merits.
Translator Stage
Usually near the amplifier input is a stage of amplification that performs the function of voltage translation -- of accommodating HV at its output node. Two possible circuits are the common-emitter (CE) and common-base (CB) transistor configurations. (Although BJTs will be used here, FETs can also be applied, taking into account relevant differences between them.) The CE translator is shown below in simplified form.
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