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Browse Prior Art Database

Fast Current Threshold Circuit

IP.com Disclosure Number: IPCOM000095250D
Original Publication Date: 1965-Oct-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Sowter, BR: AUTHOR

Abstract

The circuit produces an output change at terminal 2 only when the input current to terminal 1 exceeds a predetermined threshold.

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Fast Current Threshold Circuit

The circuit produces an output change at terminal 2 only when the input current to terminal 1 exceeds a predetermined threshold.

Under quiescent conditions, with no current applied to terminal 1, transistors T1, T2 and T3 conduct. The output at terminal 2 is at its up level. The application of input current to terminal 1 at first has little or no effect on the output from terminal 2. It merely causes a corresponding decrease in collector current of T1 and an approximately equivalent increase in emitter current of T3. The currents through resistors R3 and R4 are virtually unchanged and the output at 2 remains constant.

The input threshold is reached, however, when the input current rises sufficiently to turn off T1. Thereafter, a small increase in input current is amplified by T2 producing a large base current for T3. The latter is thus driven into hard conduction causing the output at terminal 2 to fall rapidly to its down level.

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