polarity side and an intermediate voltage source of the negative polarity side respectively tp1 tp2 tpn denote timing voltage waveforms the operational source voltage of the ic v ic is given by following equation accordingly the operational source voltage of the ic v ic is less than the output differential voltage represented by the following equation the potentials vd t and vs t appear to vary with respect to the ground voltage level as a reference it is not usually required that the operating voltage of the ic be always constant although in order to prevent erroneous operation and to reduce the possibility of noise it is preferable that sudden changes of the source voltage in a short time be avoided fig1 b shows the relationship between voltages generated in the ic of the present invention in fig1 b the voltages indicated with respect to the ground level as a reference in fig1 a are represented as vdd and vss with respect to the voltage vs t as a reference therefore the operational source voltage inside the ic corresponds to such a constant dc voltage the voltage system as shown in fig1 a can easily be obtained by preparing a pulse voltage source and a dc voltage source and by combining the two voltages utilizing pulse clamping circuits fig2 a 2b and 2c show the functional.