In simulation, an op-amp has infinite gain and infinite bandwidth. In reality, it does not. The design phase involves analyzing how finite DC gain, slew rate limiting, and thermal noise affect the overall SNR.
Delta-Sigma modulators incorporate a loop filter (integrators) and a quantizer inside a feedback loop. This loop shapes the quantization noise so that most of its power lies at high frequencies, far above the signal band. A first-order modulator achieves a 9 dB (1.5 bit) improvement per doubling of OSR. Higher-order modulators (second, third, or fourth order) achieve even steeper noise shaping: 15 dB (2.5 bits) per octave for second-order, 21 dB (3.5 bits) for third-order, and so on. delta-sigma data converters theory design and simulation pdf
Beyond Schreier & Temes, several other classics are frequently sought after in PDF format: In simulation, an op-amp has infinite gain and