A Four-Quadrant Multiplier Using Triangular Waves, Diodes, Resistors, and Operational Amplifiers

A simple scheme of switching triangular waves and measuring the average current through resistors into a low impedance summing point makes possible four-quadrant multiplication with four diodes, precisely adjusted resistors, and a means of measuring the current. A practical circuit utilizes one operational amplifier to obtain -(X+Y)/2 and a second such unit to measure the summing point current. Addition of four auxiliary diodes reduces circuit interactions and makes less stringent requirements on the diodes. A simple operational adjustment procedure is described. Also, a simple means for obtaining the precise resistance balance is outlined. Calibration does not depend upon triangular wave frequency or symmetry. The amplifiers are not required to handle the triangular wave frequencies.