A Low-voltage CMOS op amp with a rail-to-rail constant-gm input stage and a class AB rail-to-rail output stage.

J. H. Botma*, R. F. Wassenaar, R. J. Wiegerink

*Corresponding author for this work

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademicpeer-review

    28 Citations (Scopus)


    In this paper a low-voltage two-stage Op Amp is presented. The Op Amp features rail-to-rail operation and has an input stage with a constant transconductance (gm) over the entire common-mode input range. The input stage consists of an n-and a p-MOS differential pair connected in parallel. The constant gm is accomplished by regulating the tail-currents with the aid of an MOS translinear (MTL) circuit. The resulting gm is constant within 5%. The common-source output range employs a feedback circuit which also contains an MTL circuit. This feedback circuit ensures class AB operation and prevents the transistors in the output stage from cutting off. The Op Amp will be realized in a semi custom CMOS process with minimum channel lengths of 10μm. Simulations show that the minimum supply voltage is less than 2.5 V. A unity gain bandwidth of 550kHz and a DC voltage gain larger than 80 dB are feasible. The input range exceeds the supply rails, whereas the output range reaches the rails within 130 m V.

    Original languageEnglish
    Title of host publicationProceedings - IEEE International Symposium on Circuits and Systems
    Place of PublicationNew York, NY
    Number of pages4
    ISBN (Print)0780312813, 9780780312814
    Publication statusPublished - 1 Jan 1993
    EventProceedings of the 1993 IEEE International Symposium on Circuits and Systems - Sheraton Chicago Hotel & Towers, Chicago, United States
    Duration: 3 May 19936 May 1993

    Publication series

    NameProceedings - IEEE International Symposium on Circuits and Systems
    ISSN (Print)0271-4310


    ConferenceProceedings of the 1993 IEEE International Symposium on Circuits and Systems
    Country/TerritoryUnited States

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