An Integrator-Based Pipelined ADC With Digital Calibration

A 12-bit pipelined analog-to-digital converter (ADC) uses a first-stage integrator-based open-loop residue amplifier and integrator nonlinearities are foreground calibrated. In the remaining traditional closed-loop stages, gain errors and memory errors are background calibrated. Separate reference voltages are used in the first three ADC stages to reduce interstage coupling. A 0.25-μm CMOS prototype dissipates 140 mW and occupies an active area of 5 mm
²
. At 40 megasamples/s (40 MS/s), the calibration improves the spurious-free dynamic range from 51.2 to 95.1 dB and the signal-to-noise-plus-distortion ratio from 43.7 to 69.0 dB.