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Unformatted text preview: 1166 IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 29, NO. 10, OCTOBER 1994 Evolution of High-Speed Operational Amplifier Architectures Doug Smith, Mike Keen, and Arthur F. Witulski Abstract— Strengths and weaknesses of modern wide- bandwidth bipolar transistor operational amplifiers are investigated and compared with respect to bandwidth, slew rate, noise, distortion, and power. This paper traces the evolution of operational amplifier designs since vacuum tube days to give a perspective of the large number of circuit variations used over time. Of particular value is the ability to use many of these circuit design options as the basis of new amplifiers. In addition, an array of operational amplifier components fabricated on the AT&T CBIC V2 [1] process is described. This design incorporates many of the architectural techniques that Vin have evolved over the years to produce four separate operational amplifier on a single base wafer. The process design methodology requires identifying the common elements in each architecture and the minimum number of additional components required to implement four unique architectures on the array. +V I. INTRODUCTION 1 T HE approach to this work will be to review various –v topologies, to utilize previous designs, and then to fab- ricate several different designs on the special base array and to demonstrate how the designs work. Operational amplifiers have been present since before the dawn of integrated circuits [2], yet there seem to be few limits to the performance that can be obtained from these devices when matched with the optimum complementary bipolar manufacturing processes [3]. Applications for these operational amplifiers, in turn, demand ever higher performance as the circuit design and process technologies evolve to meet each new demand. In Sections II–IV, several aspects of modern high-speed +/ – 5-V operational amplifier design are discussed. Voltage- feedback and current-feedback topologies are addressed with special emphasis on how architectures have evolved over time. Multistage amplifiers, unity-gain buffers, and solutions to the low-power and low-distortion design problems are reviewed. In Sections VI–X, a detailed analysis is given of four distinct high-speed, high-performance amplifiers which were fully im- plemented on one base chip to reduce development cost. Thus, the amplifiers differ only in the metal and capacitor layers. Many of the circuits contained in this work are covered under patent protection in the United States and other coun- tries. Some of the significant patent sources have been cited especially where the patent document was the only available ManuscriptrecewedFebruary9, 1994;revisedJuly 25, 1994....
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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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