The design of high-speed pipelined analog-to-digital converters using voltage-mode sampling and current mode processing techniques

In this paper, a new structure of 8-bit CMOS pipelined analog-to-digital converter (ADC) is proposed and analyzed. In order to achieve a high conversion rate, the proposed new structure adopts voltage-mode open-loop sampling circuit and current-mode circuits to perform subtraction, sub-DAC operation, and comparison. Due to current-mode subtraction operation, the closed-loop circuit can be avoided to improve the speed performance. Moreover, current steering sub-DAC is used to enhance the sub-DAC speed. From the simulation results on the demonstrative example, the proposed pipelined ADC architecture can achieve 8-bit accuracy with a sampling rate up to 71.4 MS/s when the input signal frequency is 10 MHz. The power dissipation of the pipelined ADC is 205 mW at the conversion rate of 71.4 MS/s with a single 3.3 V power supply and 1P5M 0.25 μm CMOS process. The proposed structure can reach a higher speed if the voltage-sampling delay is reduced.