Report On The Logic Gates 6a534

SAMYAK SAU

20102011 XII - A

Records of demonstration experiments

SUBMITTED FROM

PROJECT GUIDE

Samyak Sau

Mr. Pankaj Pant

{Xii

TH

Roll no.

Samyak Sau

‘A’ (Sc.)}

{SUBJECT TEACHER}

This to certify that the project report entitled “Logic gates & Transformers” submitted by Samyak sau during the academic year 2010 – 2011 is a bonafied piece of work conducted under my supervision and guidance. The data sources have been dully acknowledged. I wish his success in all his future endeavours.

Supervised by: Mr. Pankaj Pant (PGT Physics)

Mr. P.C Prashar (Principal)

I take this opportunity to express my profound sense of gratitude and respect to all those who helped me throughout this venture. I owe my regards to Mr. P.C Prashar, Principal K.V No.1 (AFS) Pathankot for his cooperation and valuable and for giving me the opportunity to undertake this project work and providing the necessary infrastructure. I would like to express my heartfelt thanks to my revered teacher and guide Mr. Pankaj Pant for his valuable guidance, encouragement and throughout my studentship under him at the institute. This project is his visualization and owes a lot of its functionality to him. Last but not the least; I owe my overwhelming gratitude to my family and friends who gave me constant and motivation to continue with this endeavour. SAMYAK SAU XII ‘A’

Samyak Sau

S.N o.

Contents

Page No.

I.

Introduction

1

II.

Principle

2

III.

Basic Gates

3

IV.

OR Gate

4

V.

AND Gate

5

VI.

NOT Gate

6

VII.

NOR Gate

7

VIII.

NAND Gate

8

IX.

EX-OR Gate

9

X

EX-NOR Gate

10

XI

Step-Down Transformer

13

XII

Step-Up Transformer

14

XIII

Construction

15

XIV

Theory

16

A gate is defined as a digital circuit which follows some logical relationship between the input and output voltages. It is a digital circuit which either allows a signal to through as stop, it is called a gate. The logic gates are building blocks at digital electronics. They are used in digital electronics to change on voltage level (input voltage) into another (output voltage) according to some logical statement relating them. A logic gate may have one or more inputs, but it has only one output. The relationship between the possible values of input and output voltage is expressed in the form of a table called truth table or table of combinations. Truth table of a Logic Gates is a table that shows all the input and output possibilities for the logic gate. George Boole in 1980 invented a different kind of algebra based on binary nature at the logic, this algebra of logic called BOOLEAN ALGEBRA. A logical statement can have only two values, such as HIGH/LOW, ON/OFF, CLOSED/OPEN, YES/NO, RIGHT/WRONG, TRUE/FALSE, Samyak Sau

CONDUCTING/NON-CONDUCTING etc. The two values of logic statements one denoted by the binary number 1 and 0. The binary number 1 is used to denote the high value. The logical statements that logic gates follow are called Boolean expressions.

LOGIC STATES 1

0

HIGH

LOW

+v

Ov

ON

OFF

CLOS E

OPEN

RIGH WRON T G TRUE FALSE YES

NO

Any Boolean algebra operation can be associated with inputs and outputs represent

the statements of Boolean algebra. Although these circuits may be complex, they may all be constructed from three basic devices. We have three different types of logic gates .These are the AND gate, the OR gate and the NOT gate.

(a) THE

OR GATE is a

device that combines A with B to give Y as the result. The OR gate has two or more inputs and one output. The logic gate of OR gate with A and B input and Y output is shown below:

Samyak Sau

In Boolean algebra, addition symbol (+) is referred as the OR. The Boolean expression: A+B=Y, indicates Y equals A OR B. (b) THE AND GATE is a device that combines A with B to give Y as the result. The AND gate has two or more inputs and one output. The logic gate of AND gate with A and B input and Y output is shown below:

In Boolean algebra, multiplication sign (either x or.) is referred as the AND. The Boolean expression: A.B=Y, indicates Y equals A AND B. (c) THE NOT GATE is a device that inverts the inputs. The NOT is a one input and one output. The logic gate of NOT gate with A and Y output is shown below:

_ In Boolean algebra, bar symbol ( ) is referred as the NOT.

The Boolean expression: Ã =Y, indicates Y equals NOT A.

Aim: TO DESIGN AND SIMULATE THE OR GATE CIRCUIT.

Components: Two ideal p-n junction diode (D1 and D2).

Theory and Construction: An OR gate can be realize by the electronic circuit, making use of two diodes D1 and D2 as shown in the figure. Here the negative terminal of the battery is grounded and corresponds to the 0 level, and the positive terminal of the battery (i.e. voltage 5V in the present case) corresponds to level 1. The output Y is voltage at C w.r.t. earth.

The following interference can be easily drawn from the working of electrical circuit is: a) If switch A & B are open lamp do not glow (A=0, B=0), hence Y=0. b) If Switch A open B closed then (A=0, B=1) Lamp glow, hence Y=1. c) If switch A closed B open then (A=1, B=0) Lamp glow, hence Y=1. Input Input Output d) If switch A & B are A B Y closed then (A=1, B=1) Lamp glow, hence Y=1. 0 0 0

Truth Table:

Samyak Sau

1

0

1

0

1

1

1

1

1

Aim: TO DESIGN AND SIMULATE THE AND GATE CIRCUIT.

Components: Two ideal p-n junction diode (D1 and D2), a resistance R.

Theory and Construction: An AND gate can be realize by the electronic circuit, making use of two diodes D1 and D2 as shown in the figure. The resistance R is connected to the positive terminal of a 5V battery permanently. Here the negative terminal of the battery is grounded and corresponds to the 0 level, and the positive terminal of the battery (i.e. voltage 5V in the present case) corresponds to level 1. The output Y is voltage at C w.r.t. earth.

The following conclusions can be easily drawn from the working of electrical circuit: a) If both switches A&B are open (A=0, B=0) then lamp will not glow, hence Y=0. b) If Switch A closed & B open (A=1, B=0) then Lamp will not glow, hence Y=0. c) If switch A open & B closed (A=0, B=1) then Lamp will not glow, hence Y=0. d) If switch A & B both closed (A=1, B=1) then Lamp will glow, hence Y=1.

Truth Table:

Samyak Sau

Input A

Input B

Output Y

0

0

0

1

0

0

0

1

0

1

1

1

Aim: TO DESIGN AND SIMULATE THE NOT GATE CIRCUIT.

Components: An ideal n-p-n transistor.

Theory and Construction: A NOT gate cannot be realized by using diodes. However an electronic circuit of NOT gate can be realized by making use of a n-p-n transistor as shown in the figure. The base B of the transistor is connected to the input A through a resistance Rb and the emitter E is earthed. The collector is connected to 5V battery. The output Y is voltage at C w.r.t. earth.

The following conclusion can be easily drawn from the working of the electrical circuit: a) b) Y=0.

If switch A is open (i.e. A=0), the lump will glow, hence Y=1. If Switch A is closed (i.e. A=1), the lump will not glow, hence

Truth Table:

Input A

Output Y

0

1

1

0

Aim: TO DESIGN AND SIMULATE THE NOR GATE CIRCUIT.

Components: Two ideal p-n junction diode (D1 and D2), an ideal n-p-n transistor.

Theory and Construction: If we connect the output Y’ of OR gate to the input of a NOT gate the gate obtained is called NOR. The output Y is voltage at C w.r.t. earth.

In Boolean expression, the NOR gate is expressed as Y=A+B, and is being read as ‘A OR B negated’. The following interference can be easily drawn from the working of electrical circuit is: a) If Switch A & B open (A=0, B=0) then Lamp will glow, hence Y=1. b) If Switch A closed & B open (A=1, B=0) then Lamp will not glow, hence Y=0. c) If Switch A open & B close (A=0, B=1) then Lamp will not glow, hence Y=0. d) If switch A & B are closed then (A=1, B=1) Lamp will not glow, hence Y=0. Samyak Sau

Truth Table: Input A

Input B

Output Y

0

0

1

1

0

0

0

1

0

1

1

0

Aim: TO DESIGN AND SIMULATE THE NAND GATE CIRCUIT.

Components: Two ideal p-n junction diode (D1 and D2), a resistance R, an ideal np-n transistor.

Theory and Construction: If we connect the output Y’ of AND gate to the input of a NOT gate the gate obtained is called NAND. The output Y is voltage at C w.r.t. earth.

In Boolean expression, the NAND gate is expressed as Y=A.B, and is being read as ‘A AND B negated’. The following interference can be easily drawn from the working of electrical circuit: a) If Switch A & B open (A=0, B=0) then Lamp will glow, hence Y=1. b) If Switch A open B closed then (A=0, B=1) Lamp glow, hence Y=1. c) If switch A closed B open then (A=1, B=0) Lamp glow, hence Y=1. d) If switch A & B are closed then (A=1, B=1) Lamp will not glow, hence Y=0.

Truth Table: Samyak Sau

Aim: TO DESIGN AND SIMULATE THE EX OR GATE CIRCUIT.

Input A

Input B

Output Y

0

0

1

1

0

1

0

1

1

1

1

0

Components: Two AND gate, an OR gate, two NOT gate.

Theory and Construction: The operation EXOR checks for the exclusivity in the value of the two signals A and B. It means if A and B are not identical (i.e. if A=0 and B=1 or vice versa), the output Y=1, and if both are identical, then the output Y=0. This operation is also called exclusive OR gate, designated EXOR.

In Boolean expression, the EX OR gate is expressed as Y=A.B + A.B = The following interference can be easily drawn from the working of electrical circuit: a) If both switches A&B are open (A=0, B=0) then lamp will not glow, hence Y=0. b) If Switch A open B closed then (A=0, B=1) Lamp glow, hence Y=1. c) If switch A closed B open then (A=1, B=0) Lamp glow, hence Y=1. d) If switch A & B are closed then (A=1, B=1) Lamp will not glow, hence Y=0.

Truth Table:

Samyak Sau

Input A

Input B

Output Y

0

0

0

1

0

1

0

1

1

1

1

0

Aim: TO DESIGN AND SIMULATE THE EX NOR GATE CIRCUIT.

Components: Two AND gate, an OR gate, three NOT gate.

Theory and Construction: The operation EXNOR checks for the exclusivity in the value of the two signals A and B. It means if A and B are not identical (i.e. if A=0 and B=1 or vice versa), the output Y=0, and if both are identical, then the output Y=1. This operation is also called exclusive NOR gate, designated EXNOR.

In Boolean expression, the EX NOR gate is expressed as Y=A.B + A.B = The following interference can be easily drawn from the working of electrical circuit: a) If Switch A & B open (A=0, B=0) then Lamp will glow, hence Y=1. b) If Switch A closed & B open (A=1, B=0) then Lamp will not glow, hence Y=0. c) If Switch A open & B close (A=0, B=1) then Lamp will not glow, hence Y=0. d) If switch A & B both closed (A=1, B=1) then Lamp will glow, hence Y=1.

Truth Table:

Samyak Sau

Input A

Input B

Output Y

0

0

1

1

0

0

0

1

0

1

1

1

The transformer is a device used for converting a low alternating voltage to a high alternating voltage or a high alternating voltage into a low alternating voltage.

It is based on the principle of mutual induction that is if a varying current is set-up in a circuit induced e.m.f. is produced in the neighbouring circuit. The varying

current

in

varying

magnetic

a

circuit

produce

flux

which

induces

e.m.f. in the neighbouring circuit.

Samyak Sau

In this step-down transformer is used: This transformer converts high voltage at alternating current into low voltage alternating current. In step-down transformer the number of turns in primary coil remains large as compare to secondary coil.

Samyak Sau

In this step-up transformer is used: This transformer converts low voltage at alternating current into high voltage alternating current. In step-up transformer the number of turns in secondary coil remains large as compare to primary coil.

The transformer consists of two coils. They are insulated with each other by insulated material

and wound on a common core. For operation at low frequency, we may have a soft iron. The soft iron core is insulating by ing thin iron strips coated with varnish to insulate them to reduce energy losses by eddy currents.

Samyak Sau

The input circuit is called primary. And the output circuit is called secondary.

Suppose, the number of turns in

the

primary coil is NP and that in the secondary coil is NS. The resistance of the coil is assumed to be zero. Let dq /dt be the rate of change of flux in each turn of the primary coil. If Ep be the e.m.f. in the primary circuit then. EP = –NP (1) We suppose that there is no loss of flux between the primary and secondary coils. Then, the induced e.m.f. in the secondary coil will be: ES = –NS (2) From equations (i) and (ii), we find: Ns/Np = K is called transformer ratio or turn ratio. For step up transformer K > 1 For step down transformer K < 1 That is for step-up transformer NS > NP, therefore ES>EP. For the step down transformer NS < NP therefore ES < EP. Efficiency: The efficiency of the transformer is given by: Samyak Sau

If Ip and Is be the currents in the primary and secondary circuits. For ideal transformer = 1 = 100%. Therefore ES|IS = EP|IP Therefore, for step up, transformer current in the secondary is less than in the primary (IS < IP). And in a step down transformer we have IS > IP.

In practice, the output energy of a transformer is always less than the input energy, because energy losses occur due to a number of reasons as explained below. 1.

Loss of Magnetic Flux: The coupling between the coils is seldom perfect. So, whole of the magnetic flux produced by the primary coil is not linked up with the secondary coil.

2. 3.

Iron Loss: In actual iron cores in spite of lamination, Eddy currents are produced. The magnitude of eddy current may, however be small. And a part of energy is lost as the heat produced in the iron core.

4. 3. Copper Loss: In practice, the coils of the transformer possess resistance. So a part of the

energy is lost due to the heat produced in the resistance of the coil. 5.

Hysteresis Loss: The alternating current in the coil tapes the iron core through complete cycle of magnetization. So Energy is lost due to hysteresis.

6. 5. Magneto restriction: The alternating current in the Transformer may be set its parts in to vibrations and sound may be produced. It is called humming. Thus, a part of energy may be lost due to humming.

Encarta Encyclopaedia. Samyak Sau

Britannica Encyclopaedia. www.wikipedia.co m. www.answers.com . www.google.co.in.

Developed At: - Kendriya Vidyalaya no.1 (AFS), Pathankot d to CENTRAL BOARD OF SECONDARY EDUCATION New Delhi.

Samyak Sau