Abstract: Analysis of the low frequency response of automatic balancing D-C amplifier with mechanical chopper is illustrated by a typical circuit in this paper.The analysis of dynamic response of the modulation and the demodulation circuits and the auxiliary car- rier wave amplifier have been considered more in details.The analysis is based on solving difference equations since the intrinsic working process behaved by the M-D M circuits using mechanical chopper is more accurately described by difference equation other than by differential equations. In this paper,the modulation and demodulation coefficients kм and kдм of the M-D M circuits and their transfer functions are derived.Besides,an analysis is given to the R-C coupled carrier amplifier and the obtained result tells us that if the parameters of amplifier are exactly choiced,the conventional type low frequency A-C amplifier may be considered as ideal amplifier as to the amplification of modulated wave amplitudes. The results derived in the paper may be used as a guidance for selecting parameters in design such type D-C amplifiers. Selfexcited low frequency oscillation of the automatic balancing D-C amplifier used as a computing operational amplifier is discussed.