Analysis and Design of Continuous-Time Comparator

Takahiro MIKI

doi:10.1587/transele.2020CTI0001

Open Access
Analysis and Design of Continuous-Time Comparator

Takahiro MIKI

Full Text Views

178

Share
Cite this

Free PDF (1.3MB)

Summary :

Applications of continuous-time (CT) comparator include relaxation oscillators, pulse width modulators, and so on. CT comparator receives a differential input and outputs a strobe ideally when the differential input crosses zero. Unlike the DT comparators with positive feedback circuit, amplifiers consuming static power must be employed in CT comparators to amplify the input signal. Therefore, minimization of comparator delay under the constraint of power consumption often becomes an issue. This paper analyzes transient behavior of a CT comparator. Using “constant delay approximation”, the comparator delay is derived as a function of input slew rate, number of stages of the preamplifier, and device parameters in each block. This paper also discusses optimum design of the CT comparator. The condition for minimum comparator delay is derived with keeping power consumption constant. The results include that the optimum DC gain of the preamplifier is e∼e³ per stage depending on the element which dominates load capacitance of the preamplifier.

Publication: IEICE TRANSACTIONS on Electronics Vol.E104-C No.10 pp.635-642

Publication Date: 2021/10/01

Publicized: 2021/10/02

Online ISSN: 1745-1353

DOI: 10.1587/transele.2020CTI0001

Type of Manuscript: Special Section INVITED PAPER (Special Section on Analog Circuits and Their Application Technologies)

Category

Authors

Takahiro MIKI
Renesas Electronics

Keyword

comparator, continuous time, analysis, optimization, relaxation oscillator, pulse width modulator, single-slope A/D converter

Cite this

Copy

Takahiro MIKI, "Analysis and Design of Continuous-Time Comparator" in IEICE TRANSACTIONS on Electronics, vol. E104-C, no. 10, pp. 635-642, October 2021, doi: 10.1587/transele.2020CTI0001.
Abstract: Applications of continuous-time (CT) comparator include relaxation oscillators, pulse width modulators, and so on. CT comparator receives a differential input and outputs a strobe ideally when the differential input crosses zero. Unlike the DT comparators with positive feedback circuit, amplifiers consuming static power must be employed in CT comparators to amplify the input signal. Therefore, minimization of comparator delay under the constraint of power consumption often becomes an issue. This paper analyzes transient behavior of a CT comparator. Using “constant delay approximation”, the comparator delay is derived as a function of input slew rate, number of stages of the preamplifier, and device parameters in each block. This paper also discusses optimum design of the CT comparator. The condition for minimum comparator delay is derived with keeping power consumption constant. The results include that the optimum DC gain of the preamplifier is e∼e³ per stage depending on the element which dominates load capacitance of the preamplifier.
URL: https://globals.ieice.org/en_transactions/electronics/10.1587/transele.2020CTI0001/_p

Copy

@ARTICLE{e104-c_10_635,
author={Takahiro MIKI, },
journal={IEICE TRANSACTIONS on Electronics},
title={Analysis and Design of Continuous-Time Comparator},
year={2021},
volume={E104-C},
number={10},
pages={635-642},
abstract={Applications of continuous-time (CT) comparator include relaxation oscillators, pulse width modulators, and so on. CT comparator receives a differential input and outputs a strobe ideally when the differential input crosses zero. Unlike the DT comparators with positive feedback circuit, amplifiers consuming static power must be employed in CT comparators to amplify the input signal. Therefore, minimization of comparator delay under the constraint of power consumption often becomes an issue. This paper analyzes transient behavior of a CT comparator. Using “constant delay approximation”, the comparator delay is derived as a function of input slew rate, number of stages of the preamplifier, and device parameters in each block. This paper also discusses optimum design of the CT comparator. The condition for minimum comparator delay is derived with keeping power consumption constant. The results include that the optimum DC gain of the preamplifier is e∼e³ per stage depending on the element which dominates load capacitance of the preamplifier.},
keywords={},
doi={10.1587/transele.2020CTI0001},
ISSN={1745-1353},
month={October},}

Copy

TY - JOUR
TI - Analysis and Design of Continuous-Time Comparator
T2 - IEICE TRANSACTIONS on Electronics
SP - 635
EP - 642
AU - Takahiro MIKI
PY - 2021
DO - 10.1587/transele.2020CTI0001
JO - IEICE TRANSACTIONS on Electronics
SN - 1745-1353
VL - E104-C
IS - 10
JA - IEICE TRANSACTIONS on Electronics
Y1 - October 2021
AB - Applications of continuous-time (CT) comparator include relaxation oscillators, pulse width modulators, and so on. CT comparator receives a differential input and outputs a strobe ideally when the differential input crosses zero. Unlike the DT comparators with positive feedback circuit, amplifiers consuming static power must be employed in CT comparators to amplify the input signal. Therefore, minimization of comparator delay under the constraint of power consumption often becomes an issue. This paper analyzes transient behavior of a CT comparator. Using “constant delay approximation”, the comparator delay is derived as a function of input slew rate, number of stages of the preamplifier, and device parameters in each block. This paper also discusses optimum design of the CT comparator. The condition for minimum comparator delay is derived with keeping power consumption constant. The results include that the optimum DC gain of the preamplifier is e∼e³ per stage depending on the element which dominates load capacitance of the preamplifier.
ER -