DIGITAL SIGNAL REQUANTIZING CIRCUIT USING MULTISTAGE NOISE SHAPING

In a digital signal noise shaping requantization circuit formed of a first delta-sigma quantizer (main loop) for executing noise shaping of an input digital signal and a second delta-sigma quantizer (sub-loop) which receives as input signal the quantization error of a local quantizer in the first delta-sigma quantizer, and whose output signal is differentiated and added to the output signal from the first delta-sigma quantizer, the second delta-sigma quantizer includes a feedback circuit for operating on a quantization error of a local quantizer therein, with a predetermined transfer function. The output signal from the feedback circuit, in addition to being fed back to the input of the second delta-sigma quantizer, is also applied to control the operation of the first delta-sigma quantizer such as to modify the value of quantization error of the local quantizer of the first delta-sigma quantizer, for thereby ensuring stable and effective operation of the second delta-sigma quantizer even when the input digital signal attains a high amplitude.