Sunday, February 1, 2015

DIGITAL LOGIC - NAND GATE

1.10 DIGITAL LOGIC - NAND GATE


The NAND gate is a standard AND gate with the output inverted. If A and B are both logic 1’s, the output at C is a 0. Under any other com­bination, the output is 1. The notation used to express this logic statement is C = A.B and is read "C equals A AND B NOT".

 Function
The function of a NAND gate is similar to the circuit shown below. If both A and B have an input, their corresponding relays is energized causing relay K3 to be energized. This causes the switch above K3 to open resulting in no output at C. If either A or B or both A and B have no input, relay K3 is closed and there is an output at C.


Truth Table
The various combinations of inputs and the resulting outputs for the function circuit are shown.

 Timing Diagram

The timing diagram shows the resulting output at C with inputs at A and B at different times for the function circuit shown.

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