Ninth Great Lakes Symposium on VLSI
A Second-Order Sigma-Delta Modulator with Built-in VGA to Improve SNR and Harmonic Distortion
Ann Arbor, Michigan
March 04-March 06
ISBN: 0-7695-0104-4
A modified architecture of the second-order switched-capacitor modulator is proposed. A simple four-transistor variable gain attenuator is included in the architecture which continuously adjusts the reference voltage of the quantizer feedback. This improves the output SNR for small signal input and reduces the harmonic distortion for large signal input. Simulation results show that it achieves higher dynamic range and lower harmonic distortions compared with the traditional architecture.