A Design of HEMT Comparators for Ultrahigh-Speed A/D Conversion

Hiroshi WATANABE  Shunsuke NAKAMURA  Takao WAHO  

IEICE TRANSACTIONS on Electronics   Vol.E91-C   No.5   pp.688-692
Publication Date: 2008/05/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e91-c.5.688
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Fundamentals and Applications of Advanced Semiconductor Devices)
comparator,  D-latch,  HEMT,  analog-to-digital converter,  

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HEMT comparators for ultrahigh-speed A/D converters have been investigated. In particular, the transition times of the D-latch used in the comparator have been analyzed by assuming a 0.1-µm HEMT technology. It is found that for small input signals (<0.1 V), the transition time from the track to latch phase dominates the comparator operation speed. As the input signal increases, this time decreases due to the positive feedback in the latch, and the comparator speed is limited by the transition time from the latch to track phase. The transition times of 20 ps have been estimated for the present comparator.