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Four Way Exclusive OR

IP.com Disclosure Number: IPCOM000090165D
Original Publication Date: 1969-Feb-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Gersbach, JE: AUTHOR

Abstract

The circuit receives logic variables A and B and the complements of logic variables C and D and produces the Exclusive-Or function at its output. The circuit includes a current source that produces currents at two nodes 2 and 3. Each node is connected to the collector terminal of a transistor 4 or 5 that produces a current according to the value of a resistor connected in its emitter circuit and the voltage applied to its base terminal. Transistors 6 and 7 are connected with resistors 8, 9, and 10 to provide a regulated voltage at the bases of transistors 4 and 5. The voltage at the bases of transistors 4 and 5 is defined by the IR drops across resistors 9 and 10 and the base-to-emitter voltage drops of resistors 6 and 7.

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Four Way Exclusive OR

The circuit receives logic variables A and B and the complements of logic variables C and D and produces the Exclusive-Or function at its output. The circuit includes a current source that produces currents at two nodes 2 and 3. Each node is connected to the collector terminal of a transistor 4 or 5 that produces a current according to the value of a resistor connected in its emitter circuit and the voltage applied to its base terminal. Transistors 6 and 7 are connected with resistors 8, 9, and 10 to provide a regulated voltage at the bases of transistors 4 and 5. The voltage at the bases of transistors 4 and 5 is defined by the IR drops across resistors 9 and 10 and the base-to-emitter voltage drops of resistors 6 and 7. The transistors are matched such that they have similar base-to-emitter voltages drops under varying operating conditions. Transistors 11 and 12 are connected as emitter-followers. The unnumbered transistors are connected in a current switching arrangement to form the logic functions that are indicated on the associated wires. The wired connections of collector terminals produce an Or function since a current in any associated transistor produces a current at the common connection. Transistors 13 and 14 are connected to limit the voltage at the collector terminals of certain transistors to prevent saturation. Transistors 15 and 16 are connected to form an And logic function at their emitter terminal connection points of the...