A 9-bit 1.8 GS/s 44 mW Pipelined ADC Using Linearized Open-Loop Amplifiers

Abstract

This paper presents a 9-bit 1.8 GS/s pipelined analog-to-digital converter (ADC) using open-loop amplifiers. In this ADC, open-loop amplifiers are used as residue amplifiers to increase the sampling rate of the ADC with relatively low power consumption. A linearization technique is proposed to suppress the SNDR decrease caused by the nonlinearity of open-loop amplifiers. The attenuation in the capacitor digital-to-analog converter (CDAC) is utilized to calibrate the gain error of the pipelined stages. In addition, top-plate sampling is proposed to further enhance the power efficiency of the residue amplifiers. With these techniques, the ADC achieves a high sampling rate and high power efficiency. A prototype of the ADC is fabricated in 65 nm CMOS technology. An SNDR of 47 dB and a FoM of 134 fJ/conversion-step is achieved at a sampling rate of 1.8 GS/s with 900 MHz input, while consuming 44 mW from a 1.2 V supply.