山形大学紀要（工学） 第7巻 第1号（1962）115-129
Mechanical vibrators, transistors, and the other semi-conductors have been used as choppers. For the present, mechanical vibrators are superior to the other type of choppers in view of the fact that the drift of mechanical vibrators is less than that of any other type of choppers. The driving frequency of mechanical vibrator, however, is 400 c/s at most, and therefore the frequency band-width of a chopper amplifier adopted mechanical choppers is rather narrower.
The purpose of this study is to widen the frequency band-width of a chopper amplifier adopted mechanical choppers by designing a new circuit, and to analyse the frequency characteristics of this type of wide-band chopper amplifiers.
Some types of wide-band chopper amplifiers have already been published. The new circuit described in this paper, however, needs less circuit elements.
In this paper, the performance of the new circuit and of the other type of wide-band chopper amplifiers is theoretically analysed and the following theoretical results are obtained: 1) The frequency band-width of the wide-band chopper amplifier is two times wider than that of ordinary chopper amplifiers. 2) Higher harmonics of output voltage are suppressed by a proper negative feedback, when choppers act in the best condition.
Accordingly the second theoretical result means that the frequency band-width becomes much wider, if the higher harmonics are suppressed so much as it can be practically neglected.
The distortion of output waveform of ordinary chopper amplifiers is observed at the frequency higher than 10 c/s, but the new circuit furnishes the good waveform up to 20 c/s.