This document provides information about logic gates and circuits. It defines a logic gate as having one or more inputs and one output. It also defines a truth table as showing all possible input-output combinations for a logic circuit. The document then discusses common logic gates like AND, OR, NOT, NAND, NOR, and XOR gates. It provides their truth tables and descriptions. It also gives examples of applications of XOR gates like parity checking and binary to gray code conversion. Finally, it discusses positive and negative logic, logic families like bipolar and MOS, and integrated circuits.

1. G.VINOTHINI M.SC.,M.PHIL.,
DEPARTMENT OF INFORMATION TECHONOLOGY,
BON SECOURS COLLEGE FOR WOMEN,
THANJAVUR.
WELCOME TO ALL

2. LOGICGATES AND CIRCUITS
unit-2

3. GATESANDTRUTHTABLE
A Gate can thus be defined as a logic circuit with
one output and one or more inputs.
A truth table is a table that shows all the input-
output possibilities of a logic circuit. each possible
input combination of bits 0 and 1 can be examined
to determined the output.
• Logic gate voltages-high and low,
• A low voltage will mean a binary 0,and a high voltage will mean
a binary 1.

4. BASICLOGICGATES
AND
OR
NOTNAND
NOR

5. Andgate
 An AND gate is a digital
logic gate with two or more inputs
and one output that performs logical
conjunction.

6. orgate
 An OR gate is a digital logic gate with
two or more inputs and one output
that performs logical disjunction.

7. notgate
 NOT gate is also called an inverter.
 The NOT gate has only one input and
one output.
 The symbol for the inverter is

8. nand gate
 The NAND gate is the combination of
AND & NOT gates.
 To realize a NAND gate, an AND gate
is connected to an inverter.
 The inputs A ad B are AND to form
the Boolean expression AB.
 The AB is then inverted by the NOT
gate.
 Y=AB.

10. norgate
 The NOR gate is the combination of
OR and NOT gate.
 To realize a NOR gate, an inverter is
connected to the output of an OR
gate.
 The Boolean expression at the input
to the inverter is therefore A+B.
 Y=A+B.

12. exclusive-orgate
 The exclusive-OR term is often
shorted to read XOR.
 It has two inputs and one output.
 Y=AB+AB
 When A=0 and B=0
 Y=0.0+0.0=1.0+0+1=0+0 0

14. APPLICATIONSOFXORGATE
Parity checker
6-bit binary to
gray converter
Controlled
inverter

15. Parity checker
 One of applications of the XOR gates
lies in testing the parity of words.
 Even the parity means a word with an
even number of 1s.
 For example , the word 1001 has an
even parity because it contains two
1s.

17. 6-bitbinarytogray converter
 A Binary to gray code converter : the
input binary word is ABCDEF and the
output gray code number is
Y1Y2Y3Y4Y5Y6.
 If the output word is 100110.

18. Controlledinverter
 Sometimes called a programmed
inverter
 When INVERTER Is low ,it transmits
the register word to the output.
 But when INVERTER is high it
transmits the 1s complement of the
register word.
 For example , if the register contains
A5A4A3A2A1A0=110011 , Then a low
INVERTER produces.

19. EXCLUSIVE-NORGATE
 An XNOR gate (sometimes referred to
by its extended name, Exclusive
NOR gate) is a digital logic gate with
two or more inputs and one output
that performs logical equality.
 The output of an XNOR gate is true
when all of its inputs are true or when
all of its inputs are false

21. Positiveandnegativelogicgates
Positive logic gate Negative logic gate
 In this state , 1 (also
called true or ON) is
considered to be the
more positive voltage
level . Ex- +5V
 The state , 0 (also
called false or OFF) is
assigned to the less
positive level of a
digital circuits. Ex- 0V
 In this state , 1 (also
called true or ON) is
considered to be the
less positive voltage
level . Ex- 0V
 The state , 0 (also
called false or OFF) is
corresponds to the
more positive voltage
level of a digital
circuits. Ex- +5V

22. LOGICCHARACTERISTICS
The two currently available logic
families (bipolar and MOS families)
posses different characteristics,
Speed
Fan- in
Fan- out
Noise immunity
Power dissipation

23. Logic characteristics

24. Bipolarlogicfamilies
Resister - transistor logic(RTL)
Diode - transistor logic(DTL)
Transistor - Transistor
logic(TTL)
Totem - pole output

25. Flowchat

26. Logicfamilies

27. integralcircuits
 When integrated circuits are used ,
one or more complete gates or other
circuits are packaged in single
integrated- circuit (IC) container.