Analog-digital converter using an integrator

Claim 1

An analogue-digital converter comprising an integrator for integrating an input analogue during a constant time, means for switching the input of said integrator to a reference voltage of reverse polarity to said input analogue signal, means including a counter for measuring the time from the switching time of the input of the integrator to the time when the output of the integrator reaches a predetermined value by counting clock pulses by said counter so that the counting result of the counter corresponds to the analogue value of the input analogue signal, a variable frequency oscillator for deviating the repetition frequency of said clock pulses, a memory for storing the counting result of the counter until the immediately succeeding counting of the clock pulses, a comparator for comparing each counting result stored in the memory with the next counting result of the counter, a variable voltage generator for generating an output whose level varies by one step of a staircase wave in response to the compared result of the comparator, so that the repetition frequency of the clock pulses is deviated by the output of the variable voltage generator until two inputs of the comparator coincide with each other, whereby the effect of noise of any repetition frequency superposed on the input analogue signal is effectively eliminated.