NOISE-SHAPING QUANTIZERS
Noise shaping is used in four major applications:

• Oversampled delta-sigma A/D converters
• Oversampled requantizers for D/A converters
• Non-oversampled dithered noise shaping for requantization
• Non-oversampled roundoff noise shaping in digital filters

There are two goals in reshaping the quantization noise spectrum:

• push noise out of the frequency band of interest
• minimize the accumulation of noise in digital filter structures

Related applications include:

• 20-bit to 16-bit conversions in CD data
• stealing 4 bits out of 16-bits from CD data to encode auxiliary information (watermarking)

An overview of the principle of feedback quantization is given below: