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Controlled Current Gain for Integrated Circuits

IP.com Disclosure Number: IPCOM000086752D
Original Publication Date: 1976-Oct-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Epley, PR: AUTHOR [+2]

Abstract

This circuit is a current source particularly adapted for use in an integrated circuit. The source can accurately control large currents with a small control current, can be turned on and off with rapidity, and has both a low voltage drop and short-circuit protection.

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Controlled Current Gain for Integrated Circuits

This circuit is a current source particularly adapted for use in an integrated circuit. The source can accurately control large currents with a small control current, can be turned on and off with rapidity, and has both a low voltage drop and short-circuit protection.

In integrated circuits, it is relatively easy to provide uniformity for all active devices on a single chip, but the circuits on different chips are subject to wide variations in performance. For example, the beta of transistors can vary over a range of 15 to 100 between several runs. The circuit shown above provides controls to hold the current gain of a circuit within a close range so that the circuits are interchangeable.

A transistor 2 is the current gain control device and controls current from its collector source 3 to its emitter output 4. The control current to the base of transistor 2 is provided by a transistor 5 connected with its collector to the source 3 and its emitter to the base of transistor 2. A current control device 6, connected between supply 3 and the base of transistor 5, can be set to a current which will be amplified by the transistors 8, 5 and 2 to determine the output current on line 4.

Since the beta values can vary widely between chips, a feedback provision is made to limit the current gain. A third transistor 8 having its collector connected to the base of transistor 5, its base connected to the junction of the base of tra...