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# Logic Circuit

IP.com Disclosure Number: IPCOM000094604D
Original Publication Date: 1965-Mar-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 29K

IBM

## Related People

Sechler, RF: AUTHOR

## Abstract

This is a current switch logic circuit which uses complementary transistors to provide increased logical capability.

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Logic Circuit

This is a current switch logic circuit which uses complementary transistors to provide increased logical capability.

Transistors 10, 12 and 14 combine to make up an NPN current switch. Transistors 16, 18 and 20 combine to make up a PNP current switch. The basic operation is such that if one of the input transistors, e. g., 10 or 12, is rendered conductive, the grounded base transistor, e. g., 14, becomes nonconductive. This is due to the rise in potential across common emitter resistor 22. Assuming that a true logical it put is represented by an up voltage level and a negated input by a down voltage, if any of inputs A, B, C, D are present, one or more of transistors 10, 12, 16 or 18 is conductive. This will result in a potential rise across resistor 22, rendering transistor 14 nonconductive and resulting in the logical output shown at terminal 24.

On the other hand, if inputs C and D are simultaneously present, transistors 16 and 18 are both nonconductive. Thus, a positive potential is applied to the emitter-base junction of transistor 20. As a result, transistor 20 conducts and its collector potential of terminal 26 is near +V. Such indicates the desired And logical output. This configuration provides the ability to both perform a logical function with either true or complemented inputs and to provide either a true or complemented output in one stage of delay.

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