A 12-bit pipelined analog-to-digital converter (ADC) using a new integration-based open-loop residue amplifier topology is presented. The amplifier distortion is cancelled with the help of an analog linearization technique based on a tunable input-driven active degeneration. Amplifier gain and nonlinearity errors are detected in background using split-ADC calibration technique. The mismatch between the two half-ADCs is minimized by sharing the residue amplifier between the two half-ADCs and adding the calibration offset over time. Based on this "split-over-time" calibration architecture, a two-lane prototype ADC was fabricated in 28-nm CMOS that achieves 64-dB signal-to-noise + distortion ratio and 77dB spurious-free dynamic range at Nyquist input after calibration. Operating at 280 MS/s, the ADC consumes 13 mW from 1-V supply, exhibiting a Schreier figure-of-merit of 164.3 dB. By dissipating only 0.4 mW in the residue amplifiers, the linearization technique helps the ADC achieve an improvement of at least 3 dB in Schreier FoM over existing state-of-the-art ADCs with comparable architectures.

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This paper presents a closed-loop class-AB residue amplifier for pipelined analog-to-digital converters (ADCs). It consists of a push-pull structure with a ``split-capacitor'' biasing circuit that enhances its power efficiency. The amplifier is inherently quite linear, and so incomplete settling can be used to save power while still maintaining sufficient linearity. This also allows the amplifier's gain to be corrected by adjusting its bias current. When combined with digital gain-error detection, in this case the split-ADC technique, the result is a power-efficient gain calibration scheme. In a prototype pipelined ADC, this scheme converges in only 12,000 clock cycles. With a near-Nyquist input, the ADC achieves 66-dB SNDR and 77.3-dB SFDR at 53 MS/s. Implemented in 40-nm CMOS, it dissipates 9 mW, of which 0.83 mW is consumed in the residue amplifiers. This represents a 1.8x improvement in power efficiency compared to state-of-the-art class-AB residue amplifiers.@en