A low-voltage Op Amp with rail-to-rail constant-gm input stage and a class AB rail-to-rail output stage

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

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    In this paper a low-voltage two-stage Op Amp is presented. The Op Amp features rail-to-rail operation and has an @put stage with a constant transconductance (%) over the entire common-mode input range. The input stage consists of an n- and a PMOS 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 gn is constant within 5% The common-source output stage 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 1Opm. Simulations show that the minimum supply voltage is less than 2.5 V. A unity gain bandwidth of 550 kHz 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 mV.
    Original languageUndefined
    Title of host publicationProceedings International Symposium on Ciruits and Systems (ISCAS '93)
    Place of PublicationChicago-Illinois
    ISBN (Print)9780780312548
    Publication statusPublished - 3 May 1993
    EventIEEE International Symposium on Circuits and Systems, ISCAS 1993 - Chicago, Illinois
    Duration: 3 May 19936 May 1993

    Publication series



    ConferenceIEEE International Symposium on Circuits and Systems, ISCAS 1993
    Other3-6 May 1993


    • IR-15945
    • METIS-112827

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