TABLE OF CONTENTS We have arrived at the arch of this Chapter, now aware of the appealing simplicity of TL circuits, ready to review the most important commercial application of the principle, analog multipliers. A comprehensive history of the analog multiplier will be addressed in a future work. We note merely that the very first paper ever published about this form [2] leapfrogged from circuits capable of operation at only a few kilohertz, or megahertz at most, to 500MHz, without significant loss of accuracy. Since about 1970, virtually all analog multipliers and dividers have been based on translinear principles. The reason is very easily seen: unlike earlier methods, such as pulse-width-height (PHW) modulation, which utilizes the fact that the average value of a pulse is proportional to the product of its duty-cycle and its amplitude, the TL multiplier could be inexpensively fabricated in monolithic form (indeed, it absolutely required that medium to be fully developed), was as fast as any possible circuit (orders of magnitude faster than the PHW type, slowed by its averaging process) and could provide the complete function (no external capacitors were required).
During the early 70's many TL multipliers were introduced as "generic" products, most notably those from Motorola and Analog Devices, the former making available flexible and inexpensive building blocks, the latter pioneering the concept of the complete function, using thin-film (silicon-chromium) resistor technology and laser trimming to achieve very precise calibration. One or two monolithic products based on PHW were introduced...
