J. Nedved et al., A TRANSISTOR-ONLY SWITCHED-CURRENT SIGMA-DELTA A D CONVERTER FOR A CMOS SPEECH CODEC/, IEEE journal of solid-state circuits, 30(7), 1995, pp. 819-822
This paper describes the design and measurement results of a 1-b A/D c
onverter based on a transistor-only switched current (SI) second-order
sigma-delta modulator, The 1-b A/D converter was simulated and proces
sed in ES2 1.5 mu m CMOS technology, The second-order filter is based
on class AB switched current-integrators. The analog current memory ce
lls in the integrator are optimized for linear operation with a strong
class AB overlap region to avoid class B operation and cross-over dis
tortion, Measurement results on the first silicon performing 11-b reso
lution show that this circuit technique is promising for speech CODEC
A/D conversion.