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Current Drive Circuit

IP.com Disclosure Number: IPCOM000092628D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Cielo, JR: AUTHOR

Abstract

This circuit provides on and off base drive to a high frequency switching transistor. Such drive is directly proportional to the current being switched. The circuit is particularly useful in those applications where the load current varies over a wide range.

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Current Drive Circuit

This circuit provides on and off base drive to a high frequency switching transistor. Such drive is directly proportional to the current being switched. The circuit is particularly useful in those applications where the load current varies over a wide range.

The circuit limits the on base drive as a function of load current and is adjusted to provide only such base drive current which is necessary to insure saturation. Thus overdrive, which lengthens storage time and limits frequency of operation, is eliminated. The off base drive current is also controlled as a function of load current and is adjusted to minimize storage time.

Switching transistor Q1 is controlled by an input E applied to the primary winding of input transformer TD. The latter is wound such that a positive control voltage E causes transistor QA to conduct thus applying a positive turnon pulse to the base of Q1. When input E reverses. a negative turnoff pulse is applied to the base of Q1 through R2 and C2 to help speed up the turnoff of Q1. At the same time the polarity of the voltage applied to the base of transistor QB reverses turning it on to create a reverse base current through Q1 in an attempt to deplete the stored minority carriers as rapidly as possible to thus reduce the storage time.

The circuit includes transformer T which has a primary winding N1 connected in the collector circuit of Q1. Secondary windings of T N2 and N3 are connected in the collector circuits o...