introduction to logic gates
DESCRIPTION
Introduction to Logic Gates. Logical gates Inverter AND OR NAND NOR Exclusive OR (XOR) Exclusive NOR (XNOR) Draw Logic Circuit Analysis of Logic Circuit. Introduction to Logic Gates. Universal gates NAND and NOR NAND gate NOR gate Execution using NAND gate Execution using NOR gate - PowerPoint PPT PresentationTRANSCRIPT
1MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Introduction to Logic Gates
• Logical gates– Inverter– AND– OR– NAND– NOR– Exclusive OR (XOR)– Exclusive NOR (XNOR)
• Draw Logic Circuit • Analysis of Logic Circuit
2MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Introduction to Logic Gates
• Universal gates NAND and NOR– NAND gate– NOR gate
• Execution using NAND gate• Execution using NOR gate• Positive & Negative Logic• SOP Expression Execution• POS Expression Execution• Integrated Logic Circuit Family
3MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
4MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• Inverter gate
• The use of inverter: complement
5MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• AND gate
6MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• OR gate
7MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• NAND gate
8MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• NOR gate
9MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• Exclusive OR (XOR) gate
10MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Gates
• Exclusive NOR (XNOR) gate
11MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Draw Logic Gates
• When Boolean expression is obtained, we can draw logic gates
• Example:– F1 = xyz’ (use three input AND gate)
12MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Draw Logic Gates
13MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Circuit Analysis
• When logic circuit is given, we can analyze the circuit to obtain logical expression
• Example:– What is the Boolean expression for F4
14MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Logic Circuit Analysis
• What is the Boolean expression for F5
15MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Universal Gates: NAND & NOR
• Gate AND/OR/NOT is enough to build any Boolean function
• Even though, other gates is also used because:– Very useful (no choice)
– Save transistor’s number
– Self sufficient (can build any gate from it)
NAND/NOR: save, self sufficient
XOR: useful (e.g. execute parity bit)
16MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
NAND Gate
• NAND gate is self sufficient (i.e.can build any gate from it)
• Can be used for building AND/OR/NOT gate
• Build NOT gate using NAND gate
17MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
NAND Gate
• Build AND gate using NAND gates
• Build OR gate using NAND gates
18MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
NOR Gate
• NOR gate is also self sufficient
• Can be used for building AND/OR/NOT gate
• Build NOT gate using NOR gate
19MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
NOR Gate
• Build AND gate using NOR gates
• Build OR gate using NOR gates
20MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Build using NAND gate
• It is not impossible to build Boolean expression using NAND gatesSteps– Obtain sum-of-product Boolean expression
• E.g: F3 = xy’ +x’z
– Use DeMorgan theorem to get expression using two level NAND gate
• E.g: F3 = xy’ +x’z = (xy’+x’z)” = ((xy’)’.(x’z)’)’
21MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Build using NAND gate
22MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Build using NOR gate
• It is not impossible to build Boolean expression using NOR gatesSteps– Obtain product-of-sum Boolean expression
• E.g: F6 = (x+y’).(x’+z)
– Use DeMorgan theorem to get expression using two level NAND gate
• E.g: F3 = (x+y’).(x’+z) =((x+y’).(x’+z))’’ = ((x+y’)+(x’+z)’)’
23MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Build using NOR gate
24MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Positive & Negative Logic
• In logic gate, most of the time– H (High Voltage, 5V) = logic 1
– L (Low Voltage, 0V) = logic 0
• This is called positive logic• However, if it is inverted, it is negative logic
– H (High Voltage, 5V) = logic 0
– L (Low Voltage, 0V) = logic 1
• Depends, some similar gate need different Boolean function
25MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Positive & Negative Logic
• Signal which is set to logic 1 is said to be active and true
• Signal which is set to logic 0 is said to be not active and false
• The name of active high signal is always written in non-compliment form
• The name of active low signal is always written in non-compliment form
26MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Positive & Negative Logic
27MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Construction of SOP Expression
• Sum-of-product expression can be built using– Two level logic gate AND-OR– Two level logic gate AND-NOT
• Logic AND-OR gate
28MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Construction of SOP Expression
• NAND-NAND circuit (with transformation circuit)– Add two balls– Change OR with NAND
with inverted input and ball
on it’s compliment input
29MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Construction of POS Expression
• Product-of-sum expression can be built using– Two level logic gate AND-OR– Two level logic gate AND-NOT
• Logic AND-OR gate
30MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR
Construction of POS Expression
• NOR-NOR circuit (with transformation circuit)– Add two balls– Change AND with NOR
with inverted input and ball
on it’s compliment input
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