at time 3 and then the output voltage 5 is added to the voltage 6 at the next time 4 resulting in voltage 1 comparing the output shown in fig4 a with the imaginary sawtooth wave in fig1 b it is noticed that the two waveforms coincide with each other while the accumulation value of the accumulator 1 is increasing accordingly a signal without spurious components can be obtained by using the time axis information while the output sb of the integrator 12 is increasing although the level converter 25 follows the accumulator 1 in fig1 it may follow the d a converter 2 or both the accumulator 1 and d a converter 2 the amplification factor of the differential amplifier 11 or the time constant of the integrator 12 is not limited to unity since the output voltage sb of the integrator is proportional to the amplification factor or the time constant the reference voltage vr is set to match these values the two inputs to the differential amplifier 11 the subtrahend signal and the minuend signal can be exchanged in this case the output of the differential amplifier 11 becomes symmetrical to the waveform se as shown in fig1 b with respect to the axis of zero voltage and hence the outputs of both the integrator 12 and the comparator 4 are inverted thus since the output sc of the comparator 4 is an inverted version of the waveform sc as shown in fig4 b a t ff that operates at a falling edge must be used as the t ff 5 in other words the state of the t ff is reversed at each timing.