LOGIC GATES

WHAT ARE LOGIC GATES?

The Logic Gate is the simplest integrated circuit (IC). They are called logic gates because the circuits act like gates in a fence.

The gate is either open or closed depending on the conditions set.

THE BASIC LOGIC GATES AND : acts in the same

way as two switches are placed in series.

X equals A and BX= A.B

OR: operates like a circuit with two switches placed in parallel.

X equals A or BX= A+B NOT: acts in the same way

as a transistor. It is an INVERTER.

A with a bar is read as Not A

LOGIC GATES consist of diodes, transistors and resistors assembled in a silicon chip.

LOGIC GATES SYMBOL AND TRUTH TABLES

At any given time, every terminal may have an input or output of 1(high) or 0 (low). In most logic gates, the low state is approx. 0 volt, while the high state is 5 volts or 6 volts in some.

Take Note:

The inputs and outputs of logic gates are either 1 or 0 which stands for Yes or No; True or False; or high or low voltages respectively.

OTHER TYPES OF LOGIC GATES

These are the simplest combination gates derived from the basic logic gates.

NAND gate is a combination of AND and NOT gate.NOR gate is an OR and

NOT gate combination.

OTHER TYPES OF LOGIC GATES

TRUTH TABLES

TRY THIS! A system of AND gates with 5 inputs

A

B

C

D

E

What is the final output in X if A = 1 and B = 0, C = 0, D = 1 and E = 1 ?

X

TRY THIS!

A = 1 and B = 0, What is the final output at X?

X

A system of combination of gates.

A

B

C

D

Determine the output in X if A and B are both 1 and C and D are both 0?

X

TRY THIS!

TRY THIS!

LOGIC GATES SUMMARY