Immediate Calibration of Operational Ampli fier Gain Error in Pipelined ADCs Using Extended Correlated

Abstract

This paper introduces extended correlated double sampling (ECDS) as a new gain-calibration technique in pipelined analog-to-digital converters (ADCs). The proposed calibration simultaneously improves the effective dc gain and increases the maximum output swing of the opamps with given overdrive volt- ages. Furthermore, ECDS is immediate, thus avoiding the long convergence time associated wit h many background calibration schemes. This characteristic make s it desirable for applications where the ADC is on only brie fly, such as wireless sensor networks (WSNs). An 11-bit 40-MS/s prototype pipelined ADC has been fabricated in 0.25- m CMOS to demonstrate the proposed cali- bration technique. The active die area is 3.8 mm , and the analog power dissipation is 85 mW from a 2.5-V supply. With a 72-kHz input frequency, ECDS improves signal-to-noise-and-distortion ratio from 40.1 to 63.4 dB and spurious-free dynamic range from 41.8 to 75.7 dB.