The fundamental concepts of sigma-delta ADCs include Oversampling, Noise Shaping, Digital Filtering, and Decimation. The first example is a standard "Nyquist" operation for an ADC. The second illustrates oversampling by a factor of K reduces the quantization noise within the bandwidth of interest with out of band noise being removed with a digital filter. The output rate of the digital filter can then be reduced (decimated) to the original fs. Each time K is doubled, the noise in the fs/2 bandwidth is reduced by 3dB. The addition of the sigma-delta modulator shapes the quantization noise and pushes most of it outside the bandwidth of interest. This greatly increases the SNR within the DC to the fs/2 bandwidth.