Browse Prior Art Database

N Way Priority Circuit

IP.com Disclosure Number: IPCOM000073998D
Original Publication Date: 1971-Mar-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 33K

Publishing Venue

IBM

Related People

Henle, RA: AUTHOR

Abstract

This circuit is operative to select and latch the first of N-inputs which are at a positive level, ignoring subsequently received inputs until the circuit is reset.

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N Way Priority Circuit

This circuit is operative to select and latch the first of N-inputs which are at a positive level, ignoring subsequently received inputs until the circuit is reset.

Each of the N-latch circuits comprise respective input terminals I1 ... In connected to diodes D1 ... Dn, NPN transistors A1 ... An, and PNP transistors B1 ... Bn. A reset input terminal 15 is connected to resistor R3 and the common emitter line 20. Transistor 22 is conductive during a portion of the circuit operation and provides one current path for the single current source designated as I, constituted by the signal received at I and resistor R3.

In operation, when reset input terminal 15 is at a negative potential, the first input which has a positive signal applied at terminal I1 ... In will be latched. Transistor 22 will remain conducting until such time as one of the I1 ... In inputs causes the base of the AX transistor to go positive where X goes from 1 to n.

The circuit will then latch on this input. For example, assuming that all inputs I1 through In are at ground potential or less and the reset terminal 15 is at a negative potential, then current I is flowing in resistor R3. However, when input I1 begins to go positive the base of transistor A1 is also raised to the positive potential. This causes the current I which had been flowing in the emitter of transistor 22 to now switch to the emitter of transistor A1. Consequently, collector current in transistor A1 will now flow through resistor R10 causing the base of transistor B1 to be at a negative potential relative to its emitter potential. Thus, the collector current of transistor B1 will raise the base potential of transistor...