Logic gates

• Basic Logic gates:
  • NOT, AND, OR, NOR, NAND, XOR
• Within them, NAND and NOR are said to be universal
  • with NAND / NOR you can build any other gates

Exercise: With NAND gate only, build NOR gate

In ICs (CPU, RAM etc)

• The circuit is most likely build with NAND gates only
  • NAND gates have better performance than NOR
• Keeping all building blocks in IC (Integrated circuit) the same so the cost will be cheaper / easier to manufacturer

Flip-flops

SR/JK flip-flop

• Sometimes it's called a 'latch'
• A sequential circuit which output depends on the input and previous output

Simplifying Circuit using Boolean Expression

1. Write Circuit in Boolean Expression
2. Simplify the Expression
3. Redraw the simplified circuit
4. Verify in Truth Table

Simplify the followings