High-gain microwatt composite cascode op amps |
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Authors: | Rishi Pratap Singh Taylor Waddel Donald T. Comer Kent Layton |
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Affiliation: | 1. ON Semiconductor , 629 Quality Drive, American Fork , Utah 84003-3362 , USA;2. Department of Electrical and Computer Engineering , Brigham Young University , 459CB, Provo , Utah 84602 , USA |
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Abstract: | This article discusses the composite cascode stage, both single-ended and differential, operating in the weak inversion or moderate inversion region. The gain of the MOS composite cascode differential stage can exceed 100,000?V/V, a figure that has never been reported in the literature. For low-frequency applications, this configuration can be used to fabricate op amps that have high-gain, low-power and low-nonlinear distortion. Two different architectures, both having two gain stages are reported. The first op amp uses the Widlar architecture to achieve a gain of 117?dB, a power dissipation of 110?µW and uses a compensation capacitor of only 3.5?pF. The second op amp uses a class AB stage for the second and final stage and utilises the parasitic capacitance at the output of the first stage for compensation. This self-compensating op amp has a gain of 110?dB and a power dissipation of 21?µW. |
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Keywords: | composite cascode CMOS op amp weak inversion subthreshold operation high-gain low-power |
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