A novel highly stable high-resolution oversampled Σ-Δ A/D converter configuration

Feedforward and multiple-feedback Σ-Δ A/D converters offer high-resolution, but are susceptible to instability in the presence of capacitor tolerances in a corresponding switched capacitor (SC) hardware implementation. The hitherto Σ-Δ A/D converters are usually based on: (a) complementary signal and noise transfer functions; and/or (b) unit-circle noise transfer function zeros. This paper is concerned with the development of a novel Σ-Δ A/D converter having, instead, magnitude-squared or magnitude-complementary signal and noise transfer functions. The proposed A/D converter exhibits resolution and dynamic range properties similar to those of the existing feedforward and multiple-feedback A/D converters, but offers increased stability performance in the presence of capacitor tolerances in the SC hardware implementation. In addition, the SC hardware implementation of the resulting A/D converter leads to a capacitance spread which is comparable to that of hitherto Σ-Δ A/D converters