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Fast Rise Final Circuit for Inductive Load Current Regulator

IP.com Disclosure Number: IPCOM000091327D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Redfield, AG: AUTHOR

Abstract

This is a high-speed current regulator for an inductive load. During quiescent operation, transistor Q2 is biased off. Current supplied by source B1 flows through Q1 which is regulated by feedback through DC differential amplifier A. At this time, the voltage across shunt T, applied at input X of amplifier A, equals the reference voltage at point V1 set by potentiometer R1 and applied to the other input of amplifier A. Resistors R3 and R4 provide degeneration for transistors Q1 and Q2. Diode D2 prevents excessive base-to-emitter voltage from damaging Q2.

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Fast Rise Final Circuit for Inductive Load Current Regulator

This is a high-speed current regulator for an inductive load. During quiescent operation, transistor Q2 is biased off. Current supplied by source B1 flows through Q1 which is regulated by feedback through DC differential amplifier
A. At this time, the voltage across shunt T, applied at input X of amplifier A, equals the reference voltage at point V1 set by potentiometer R1 and applied to the other input of amplifier A. Resistors R3 and R4 provide degeneration for transistors Q1 and Q2. Diode D2 prevents excessive base-to-emitter voltage from damaging Q2.

When reference voltage V1 is increased by moving switch S to potentiometer R2, amplifier A increases the base voltage of Q1 causing it to conduct at saturation so that its collector voltage decreases. The base-to-emitter voltage of Q2 is increased sufficiently to conduct at saturation. The voltage at point V2 goes negative because of storage condenser C. The latter is kept charged by source B2 and resistor R5 and is virtually grounded through Q1 and Q2. Current is then supplied to inductive load L through C, Q1 and Q2, and source B1, and diode D1 is cut off by the large negative voltage at point V2. The current increases at a rate (B1+B2) L until the voltage across shunt T equals the voltage at point V1. At that time, the output voltage of amplifier A decreases until Q2 is cut off and current is again regulated by Q1 through diode D1.

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