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Ultra-low-power time-efficient circuitry of dual comparator/amplifier for SAR ADC by CMOS technology

Muhammad Yasir Faheem (Beijing Institute of Technology, Beijing, China)
Shun'an Zhong (Beijing Institute of Technology, Beijing, China)
Xinghua Wang (Beijing Institute of Technology, Beijing, China)
Muhammad Basit Azeem (University of Engineering and Technology Faisalabad Campus, Faisalabad, Pakistan)

Circuit World

ISSN: 0305-6120

Article publication date: 3 February 2020

Issue publication date: 18 June 2020




Successive approximation register (SAR) analogue to digital converter (ADC) is well-known with regard to low-power operations. To make it energy-efficient and time-efficient, scientists are working for the last two decades, and it still needs the attention of the researchers. In actual work, there is no mechanism and circuitry for the production of two simultaneous comparator outputs in SAR ADC.


A small-sized, low-power and energy-efficient circuitry of a dual comparator and an amplifier is presented, which is the most important part of SAR ADC. The main idea is to design a multi-dimensional circuit which can deliver two quick parallel comparisons. The circuitry of the three devices is combined and miniaturized by introducing a lower number of MOSFET’s and small-sized capacitors in such a way that there is no need for any matching and calibration.


The supply voltage of the proposed comparator is 0.7 V with the overall power consumption of 0.257mW. The input and clock frequencies are 5 and 50 MHz, respectively. There is no requirement for any offset calibration and mismatching concerns due to sharing and centralization of spider-latch circuitry. The total offset voltages are 0.13 0.31 mV with 0.3VDD to VDD. All the components are small-sized and miniaturized to make the circuit cost-effective and energy-efficient. The rise and response time of comparator is around 100 ns. SNDR improved from 56 to 65 dB where the input-referred noise of an amplifier is 98mVrms.


The proposed design has no linear-complexity compared with the conventional comparator in both modes (working and standby); it is ultimately intended and designed for 11-bit SAR ADC. The circuit based on three rapid clock pulses for three different modes includes amplification and two parallel comparisons controlled and switched by a latch named as “spider-latch”.



Faheem, M.Y., Zhong, S., Wang, X. and Azeem, M.B. (2020), "Ultra-low-power time-efficient circuitry of dual comparator/amplifier for SAR ADC by CMOS technology", Circuit World, Vol. 46 No. 3, pp. 183-192.



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