Browse Prior Art Database

Logic Level Equal Compare Circuit

IP.com Disclosure Number: IPCOM000094975D
Original Publication Date: 1965-Jul-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Wallace, LJ: AUTHOR

Abstract

The equal-compare circuit is an Exclusive Or circuit comprising a diode bridge 1 and a pair of transistors T2 and T3. T2 and T3 are connected in series between ground potential and a negative supply terminal. Output terminal Z is connected to the collector of T2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 100% of the total text.

Page 1 of 2

Logic Level Equal Compare Circuit

The equal-compare circuit is an Exclusive Or circuit comprising a diode bridge 1 and a pair of transistors T2 and T3. T2 and T3 are connected in series between ground potential and a negative supply terminal. Output terminal Z is connected to the collector of T2.

Bridge 1 includes diodes D1...D4, resistor R1 and input terminals A and B. D3 and D4 connect A and B to the base of T3 by way of resistor R2. D1 and D2 connect A and B to the base electrode of T2 by way of a diode D5 and a parallel- connected capacitor C1 and resistor R3. Diode D6 is connected across the base-emitter junction of T2.

When ground potential is applied to A and B, T2 and T3 are cut off by reason of similar potentials being applied to their bases and emitters. Similarly, when negative potentials are applied to A and B, T2 and T3 are turned off. In both instances, Z is at -12 volts. However, when a negative potential is applied to A or B and ground potential is applied to the other terminal, ground potential is applied to the base of T3 and the negative potential is applied to the base of T2 to turn both transistors on driving output Z to ground potential. Z can be connected to the collectors of other equal-compare circuits for the comparison of more than two signals.

1

Page 2 of 2

2

[This page contains 1 picture or other non-text object]