Two-step multi-stage incremental ADC

Multi-stage noise-shaping (MASH) is a useful technique for the design of stable high-order ΔΣ modulators. A two-step MASH incremental ADC (IADC) is proposed. In the first step it performs a third-order coarse quantisation. Using the same hardware, in the second step the circuit performs fine quantisation as a second-order IADC. Thus, it achieves fifth-order noise shaping with only three amplifiers. For an oversampling ratio OSR = 32, the signal-to-noise ratio can be boosted by about 30 dB. The scheme is suitable for wide bandwidth applications.