Sturdy MASH D-S modulator

Introduction: With delta-sigma (D-S) modulators (DSMs) heading towards low-power high-speed applications with low oversampling ratio (OSR), the employing of higher-order noise shaping is necessary to achieve the desired signal-to-noise-and-distortion ratio (SNDR). The single-loop high-order DSM can provide the required SNDR with relaxed analogue circuit requirements, but is prone to loop instability. On the other hand, the multi-stage noise shaping (MASH) structure guarantees stable operation, but it requires high accuracy integrators to minimise the quantisation error leakage resulting from analogue–digital filter mismatches. These integrators are often implemented using powerhungry multi-stage operational amplifiers (opamps). The new, sturdy MASH (SMASH) structure presented in this Letter obviates the matching requirement, and thus allows using low-gain opamps for low-power high-speed operation.