VARIABLE, ADAPTIVE QUANTIZATION IN SIGMA-DELTA MODULATORS

An improved sigma-delta modulation technique that may be employed in a sigma-delta Digital-to-Analog Converter (DAC) to convert digital signals into corresponding analog signals over a wide signal range and with high linearity. The sigma-delta DAC comprises a sigma-delta modulator including a variable quantizer and a quantizer controller, and an internal DAC. The sigma-delta modulator adaptively quantizes the digital input signal to a first number p of quantization levels. Next, the quantizer controller controls the variable quantizer to correlate the p quantization levels to the amplitude of the digital input signal, thereby generating a second number q of quantization levels. The internal DAC then receives the q quantization levels from the variable quantizer one group of p levels at a time, and produces an analog output signal therefrom that corresponds to the digital input signal.