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BASE DRIVE CIRCUIT WITH CONTROLLED dIdt FOR SWITCHING APPLICATIONS

IP.com Disclosure Number: IPCOM000060382D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Ahmed, S: AUTHOR [+2]

Abstract

A control circuit is disclosed which provides high base drive and control dIdt by using a combination of resistors which slows the transition rate. The circuit eliminates the feedback capacitor and employs a basic RC (resistor-capacitor) time constant approach to limit the output transistor current. Different technologies have used various schemes to control dVdt and dIdt of a 1 V/ns general-purpose circuit. In some instances a feedback capacitor is used or a feedback pair of transistors. This circuit uses a resistor combination which has both a better control of dIdt as well as a tighter tolerance. It provides a higher base drive with practically no change in dIdt. Fig. 1 shows a schematic of the circuit with the resistors shown with their specific values indicated. This circuit can provide a dIdt as low as 7.

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BASE DRIVE CIRCUIT WITH CONTROLLED dIdt FOR SWITCHING APPLICATIONS

A control circuit is disclosed which provides high base drive and control dIdt by using a combination of resistors which slows the transition rate. The circuit eliminates the feedback capacitor and employs a basic RC (resistor-capacitor) time constant approach to limit the output transistor current. Different technologies have used various schemes to control dVdt and dIdt of a 1 V/ns general-purpose circuit. In some instances a feedback capacitor is used or a feedback pair of transistors. This circuit uses a resistor combination which has both a better control of dIdt as well as a tighter tolerance. It provides a higher base drive with practically no change in dIdt. Fig. 1 shows a schematic of the circuit with the resistors shown with their specific values indicated. This circuit can provide a dIdt as low as 7.7 mA/ns with 0.58 V/ns transition under nominal conditions. A worst-case condition will yield a low dIdt of 12.8 mA/ns for a 0.95 to 1 V/ns transition. In this circuit dIdt is primarily a function of the value of resistors R2 and R4 as follows: A 25% increase in R2 decreases the dIdt by 12%. A 25% decrease in R2 increases the dIdt by 20%. A 25% increase in R4 decreases the dIdt by 11%. A 25% decrease in R4 increases the dIdt by 16%. R3 can be decreased to increase the base drive to transistor T3 with practically no change in dIdt. R5 can be increased or decreased 25% with no significant chan...