Browse Prior Art Database

Negative and Logic Functions Circuit

IP.com Disclosure Number: IPCOM000090536D
Original Publication Date: 1969-May-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

Dorler, JA: AUTHOR

Abstract

Logic input signals are received at a plurality of input terminals 10 and transmitted to the base of transistor 12 via a plurality of coupling diodes 14. The emitter of transistor 12 is connected to the base of output transistor 16 by way of diode 18. Operating potentials are provided by source +V at terminal 20 in conjunction with a plurality of biasing resistors R1...R4. Terminal 25 is an And extend point to which additional input diodes can be connected. Terminal 26 is a Or extend point to which additional input diodes can also be connected. With a positive voltage, approximately 1.5 volts or greater, applied to all terminals 10, transistors 12, 16, and diode 18 are in a conductive state. This causes the voltage at terminal 28 to decrease so as to equal the saturation voltage of transistor 16.

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Negative and Logic Functions Circuit

Logic input signals are received at a plurality of input terminals 10 and transmitted to the base of transistor 12 via a plurality of coupling diodes 14. The emitter of transistor 12 is connected to the base of output transistor 16 by way of diode 18. Operating potentials are provided by source +V at terminal 20 in conjunction with a plurality of biasing resistors R1...R4. Terminal 25 is an And extend point to which additional input diodes can be connected. Terminal 26 is a Or extend point to which additional input diodes can also be connected. With a positive voltage, approximately 1.5 volts or greater, applied to all terminals 10, transistors 12, 16, and diode 18 are in a conductive state. This causes the voltage at terminal 28 to decrease so as to equal the saturation voltage of transistor 16. When any terminal 10 is reduced to a voltage of approximately .5 volts or less, the potential on line 24 drops such that transistors 12, 16, and diode 18 are not conducting. In this state, the potential of output terminal 28 approaches the voltage of terminal 22. The combination of biasing resistors R1, R2, and R3, in conjunction with the operating potential +V, causes node 22 to go positive when the inputs are switched to a relatively negative state so as to increase turnoff time of transistor 16. The use of an emitter-follower output transistor 16 also increases turnoff time for a given circuit power dissipation.

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