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760 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. SC-13, NO. 6, DECEMBER 1978 High-Performance NMOS Operational Amplifier DANIEL S13NDEROWICZ, STUDENT MEMBER, IEEE, DAVID A. HODGES, FELLOW, IEEE, AND PAUL R. GRAY, SENIOR MEMBER, IEEE Abstract-A high-performance operational amplifier 300 milz in area has been designed and fabricated in a standard n-channel silicon-gate enhancement/depletion MOS process. Specifications achieved include open-loop gain, 1000; power consumption, 10 mW; common-mode range within 1.5 V of either supply rail; unity-gain bandwidth, 3.0 MHr with 80° phase margin; rms input noise (2.5 Hz-46 kHz), 25 wV; C-message weighted noise -5 dBmC, and O.I-percent settling time, 2.5 MS. I. INTRODUCTION o PERATIONAL amplifiers are necessary elements in LSI analog components such as charge-coupled device filters [1], analog-to-digital converters [2], and sampled-data recursive and state variable filters [3], [4]. This paper describes a high-performance operational amplifier realized in a standard n-channel silicon-gate MOS process. This amplifier offers better performance, lower power consumption, and requires less silicon chip area than previous designs [5]. Compared to bipolar transistors, MOS transistors exhibit lower transconductance per unit supply current, poorer device matching, and higher equivalent input noise levels. On the other hand, IvlOS transistors are superior aslow-offset analog switches and high input impedance amplifying devices. Modern MOS processes employing local oxidation, high-resistivity substrates, and self-aligned device structures show extremely small parasitic capacitances and provide very high analog circuit density. Through proper use of the analog memory capability of MOS sampled-data circuits, the effects of device mismatching and flicker (1 /fl noise can be greatly reduced, Overall, the per- formance of analog LSI based on MOS technology can match or surpass that of circuits based on bipolar technology in many applications, while providing markedly higher levels of integration. II. CIRCUIT REQUIREMENTS The operational amplifier described here is intended for use at audio frequencies. One to twenty or more amplifiers may be incorporated on a larger analog MOS LSI chip. An open- loop dc voltage gain greater than 1000 is typically needed to provide closed-loop gain accuracy on the order of 0.1 percent. A unity-gain bandwidth greater than 2 MHz is necessary if the Manuscript received October 1, 1977; revised July 30, 1978. This research was supported by U.S. Army Research Office Grant DAAG29- 76-G-0244. The authors are with the Department of Electrical Engineering and Computer Sciences, University of California, Berkeley, CA 94720. amplifier is to be useful throughout the audio frequency range. This requirement was to be met with internal phase compensa- tion adequate to assure stability under all conditions. It was desired that the output be capable of driving at least 1 V rms into a 1000-C? external load, and 2 V rms into a high-im- pedance load, but quiescent dc power consumption was required to be less than 20 mW. Common-mode rejection
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This note was uploaded on 09/19/2010 for the course EE 7326 taught by Professor Jimhellums during the Spring '08 term at University of Texas at Dallas, Richardson.

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