LOGIC GATES

• Logic gate is an idealized model of computation or physical electronic Device implementing a Boolean function ,a logical operation performed on one or more binary inputs that produces a single binary output.

• Depending on the context ,the term may refer to an ideal logic gate ,one that has for zero rise time and unlimited fan out, or it may refer a non ideal physical device.

Example :

1. AND

2. OR

3. NAND

   1. NOR

4. XOR

5. XNOR

Symbol

A symbol is a mark, sign ,or word that indicates ,signifies, or is understand as representing an idea, object or relationship.

Truth Table

A truth table is a mathematical table used in logic specifically in connection with Boolean functions and propositional calculus.

Boolean Expression

Is an expression used to programming languages that produce a Boolean value when evaluated. Boolean value either true or false.

AND Gate

• The AND gate is a basic digital logic gate that implements logical conjunction

• An AND gate accepts two input signals.

• If the two input values for an AND gate are both 1,the output is 1, otherwise the output is 0.

Boolean Expression A.B = C

Truth Table

OR Gate

Expression A+B= C

Truth Table

NOT Gate

• By definition ,

if the input value for a NOT gate is 0, the output is 1, and if the input value is 1,the output is 0.

• A NOT gate is sometimes referred to as an inverter because it inverts the input value.

Boolean Expression A=Y

NAND Gate

• NAND gate (NOT-AND) is a logic gate which produces an output which is false only if all its inputs are true; thus its output is complement to that of an AND gate.

• A LOW (0) output results only if all the inputs to the gate are HIGH (1); if any input is LOW (0), a HIGH (1) output results. A NAND gate is made using transistors and junction diodes.

Symbol

XOR Gate

• An XOR gate produces 0 if its two inputs are the same , and a 1 otherwise.

• Note the difference between the XOR gate and the OR gate ,they differ only in one input situation.

• When both input signals are 1,the OR gate produces a 1 and the XOR produces a 0.

NOR Gate

• The NOR gate is a digital logic gate that implements logical NOR.

Boolean Expression C= A+B

XNOR Gate

• The XNOR gate (sometimes ENOR, EXNOR or NXOR and pronounced as Exclusive NOR) is a digital logic gate whose function is the logical complement of the Exclusive OR (XOR) gate.

• A high output (1) results if both of the inputs to the gate are the same. If one but not both inputs are high (1), a low output (0) results.

Boolean Expression Y = A+B

Logic Gates.pdf

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References

• https://en.wikipedia.org/wiki/Logic_gate

• http://anh.cs.luc.edu/150/notes/hardware.pdf

• https://en.wikipedia.org/wiki/XNOR_gate

Tutorial created by Kameshka Sanju