A High-Speed Analogue Multiplier

Abstract

A transistor multiplier using the variable area wave form method is described. A bandwidth of 10kc/s and an accuracy better than 1 per cent are obtained using medium-speed switching transistors. A long-tailed pair circuit varies the emitter currents of a symmetrical emitter-coupled multivibrator, which generates a pair of anti-phase rectangular waveforms, with a mark-to-space ratio dependent upon one multiplicand. A voltage dependent upon the other multiplicand is applied to two switches controlled by the waveforms from the multivibrator. The outputs of these switches are combined and smoothed to give the required product.