Ho-An Au

Document Type

Thesis - Open Access

Award Date

1972

Degree Name

Master of Science (MS)

Department / School

Electrical Engineering

Abstract

Transistors with current gains of 1,000 to 10,000 at collector current levels as low as 1 µA can now be made in discrete and in monolithic form. These devices are generally called super-beta or super-gain transistors. It is well-known that a narrow base width results in a high-beta transistor. As the emitter is diffused more deeply into the base, reducing the base width, the current gain will increase. But there is a trade-off between breakdown voltage and current gain. When the emitter is deeply diffused, the depletion region of the collector-base junction may penetrate the base and reach through to the emitter, resulting in a collector-emitter short. However, by stopping the emitter diffusion in time, a super-beta transistor can be practically made. The super-beta transistor has the disadvantage of collector-to-emitter voltage breakdown of less than 5.0 volts. This unusually low breakdown voltage precludes its use in standard circuit designs. However, it can be fabricated simultaneously with high-voltage transistors. It has been shown that circuit techniques are available, namely bootstrapping and cascode connections, that take advantage of the high-current gain of one transistor type and the high breakdown voltage of the other, producing the equivalent of a high gain, high voltage device. This transistor is a new device. It has application in the first stage of an operational amplifier. The device requires low bias currents so the undesired output offset voltage can be minimized, and the high current gain can be important to minimize noise. The goal of this research is to study the parameters of the super-beta transistor de characteristics, small signal behavior, large signal behavior, and noise - in order to better understand the device. Two types of super-beta transistors are used in this research. They are both discrete npn devices; type IT124 super-beta dual monolithic silicon planar transistor and type PR1 super-beta transistor. The IT124 is made by Intersil Incorporated and is available· commercially; the type PR1 is a development sample produced by National Semiconductor.

Library of Congress Subject Headings

Transistors
Transistor circuit

Format

application/pdf

Number of Pages

100

Publisher

South Dakota State University

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