Switching transistors used as a substitute for mechanical low-level choppers

ONE of the interesting possibilities of using transistors as switches would be to replace mechanical vibrators or choppers in the input of d-c amplifiers. The ability of transistor switches to function with emitter-collector voltages of the order of 1 millivolt or less led to a further investigation of transistor-switching behavior at these very low levels. Peculiarities of circuits utilizing transistors as switches at these low levels are discussed and possible methods of compensating for these peculiarities are presented. Effects of temperature on behavior were also investigated and it was found that, by suitably matching pairs of transistors, the effects of temperature from -50 to +90 degrees centigrade (C) were practically negligible for germanium transistors.