Abstract: A modulator is provided for converting an analog input to an output pulse train having an average amplitude proportional to the input signal. The modulator circuit employs delta-minus-sigma modulation in which the output pulse train controls the selection of reference signals which exactly balance the input signal, over time. Instantaneous differences between the reference signals and the input signal are accumulated and measured by an integrator/comparator circuit. A high level of accuracy is achieved in the integrator/comparator because the system employs offset compensation to correct for voltage offset in one or more of the operational amplifiers. Several embodiments of the offset compensation system are disclosed. A method of modulation is also disclosed.