Introduction to Logic Gates

1. Introduction to Logic Gates • Logical gates • Inverter • AND • OR • NAND • NOR • Exclusive OR (XOR) • Exclusive NOR (XNOR) • Draw Logic Circuit • Analysis of Logic Circuit MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

2. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

3. Logic Gates MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

4. Logic Gates • Inverter gate • The use of inverter: complement MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

5. Logic Gates • AND gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

6. Logic Gates • OR gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

7. Logic Gates • NAND gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

8. Logic Gates • NOR gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

9. Logic Gates • Exclusive OR (XOR) gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

10. Logic Gates • Exclusive NOR (XNOR) gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

11. Draw Logic Gates • When Boolean expression is obtained, we can draw logic gates • Example: • F1 = xyz’ (use three input AND gate) MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

12. Draw Logic Gates MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

13. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

14. Logic Circuit Analysis • What is the Boolean expression for F5 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

15. 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) MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

16. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

17. NAND Gate • Build AND gate using NAND gates • Build OR gate using NAND gates MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

18. NOR Gate • NOR gate is also self sufficient • Can be used for building AND/OR/NOT gate • Build NOT gate using NOR gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

19. NOR Gate • Build AND gate using NOR gates • Build OR gate using NOR gates MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

20. Build using NAND gate • It is not impossible to build Boolean expression using NAND gates Steps • 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)’)’ MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

21. Build using NAND gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

22. Build using NOR gate • It is not impossible to build Boolean expression using NOR gates Steps • 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)’)’ MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

23. Build using NOR gate MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

24. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

25. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

26. Positive & Negative Logic MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

27. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

28. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

29. 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 MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR

30. 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 ”: MOHD. YAMANI IDRIS/ NOORZAILY MOHAMED NOOR