2014
Physics Investigatory Project
CONTENTS
1. Certificate 2. Acknowledgement 3. Aim of the project 4. Objective 5. Summary 6. Introduction 7. Experiment
Apparatus
Theory
OR – GATE
AND – GATE
NOT GATE
Procedure
8. Application of Logic gates 9.
Bibliography
PAGE NO.
Certificate
This is to certify that ________________________________________ has satisfactorily completed his chemistry investigatory project as prescribed by the AISSC course during the academic year 2014-2015.
Teacher in charge
Internal Examiner
Date:
External Examiner
Acknowledgement
I would like to sincerely and profusely thank my chemistry teacher MR.________________________(Physics), for his able guidance and support in completing my project. I
would
also
like
to
extend
my
gratitude
to
the
principal
MR______________________________________ for providing me with all the facility that was required. Last but not the least, I would extend my gratitude towards all teaching and non teaching staff of ________________________________________ and towards my friends who has supported me to complete this project.
___________________________
Objective
: To design an appropriate Logic Gate combination for a given truth
table.
Summary : Since the 1990s, most logic gates are made in CMOS technology (i.e. NMOS and PMOS transistors are used). Often millions of logic gates are packaged in a single integrated circuit. There are several logic families with different characteristics (power consumption, speed, cost, and size) such as: RDL (resistor-diode logic), RTL (resistor-transistor logic), DTL (diode-transistor logic), TTL (transistor-transistor logic) and CMOS (complementary metal oxide semiconductor). There are also subvariants, e.g. standard CMOS logic vs. advanced types using still CMOS technology, but with some optimizations for avoiding loss of speed due to slower PMOS transistors. Non-electronic implementations are varied, though few of them are used in practical applications. Many early electromechanical digital computers, such as the Harvard Mark I, were built from relay logic gates, using electromechanical relays. Logic gates can be made using pneumatic devices, such as the Sort berg relay or mechanical logic gates, including on a molecular scale. Logic gates have been made out of DNA (see DNA nanotechnology) and used to create a computer called MAYA (see MAYA II). Logic gates can be made from quantum mechanical effects (though quantum computing usually diverges from Boolean design). Photonic logic gates use non-linear optical effects. In principle any method that leads to a gate that is functionally complete (for example, either a NOR or a NAND gate) can be used to make any kind of digital logic circuit. Note that the use of 3-state logic for bus systems is not needed, and can be replaced by digital multiplexers.
Introduction : In electronics, a logic gate is an idealized or physical device implementing a Boolean function; that is, it performs a logical operation on one or more logical inputs, and produces a single logical output. Depending on the context, the term may refer to an ideal logic gate, one that has for instance zero rise time and unlimited fan-out, or it may refer to a non-ideal physical device (see Ideal and real opamps for comparison). Logic gates are primarily implemented using diodes or transistors acting as electronic switches, but can also be constructed using electromagnetic relays (relay logic), fluidic logic, pneumatic logic, optics, molecules, or even mechanical elements. With amplification, logic gates can be cascaded in the same way that Boolean functions can be composed, allowing the construction of a physical model of all of Boolean logic, and therefore, all of the algorithms and mathematics that can be described with Boolean logic. Logic circuits include such devices as multiplexers, registers, arithmetic logic units (ALUs), and computer memory, all the way up through complete microprocessors, which may contain more than 100 million gates. In practice, the gates are made from field-effect transistors (FETs), particularly MOSFETs (metal–oxide–semiconductor field-effect transistors). Compound logic gates AND-OR-Invert (AOI) and OR-AND-Invert (OAI) are often employed in circuit design because their construction using MOSFETs is simpler and more efficient than the sum of the individual gates. In reversible logic, Toffoli gates are used.
Experiment:
Apparatus Required: The following things required are
Theory:
2 Batteries – 6 Volts
2 Switches
Torch bulb and connecting wires
Connecting Wires
The three basic logic gates and their combination are the
building block of the digital circuit.
OR-GATE : The symbol and the truth table for OR-GATE are shown in figure 1.
Figure 1
Inputs
Outputs
A
B
Y= A + B
0
0
0
1
0
1
0
1
1
1
1
1
AND-GATE : The symbol and truth table for AND-GATE are shown in figure 2.
Inputs
Outputs
A
B
Y= A + B
0
0
0
1
0
0
0
1
0
1
1
1
NOT-GATE : The symbol and truth table for NOT-GATE are shown in the figure 3.
Input
Output
A
Y=
0
1
1
0
.
A
Procedure: 1. Write product term for each input (minterm) Combination where Boolean function has output 1. While writing minterm, complement that variable whose vaiue is 0. Otherwise write it in direct form (without complement). 2. Add all the minterms to obtain the Boolean function. 3. Draw the circuit using BASIC LOGIC gates. Example: (a)
X
Y
F
Minterm
0
0
1
X. Y
0
1
0
-
1
0
0
-
1
1
1
X.Y
The Boolean function F (X,Y) is obtained as;-
F(X, Y) = X . Y + X.Y .*. Logic circuit is:
(b)
X
Y
Z
F Mintern
0
0
0
0
0
0
1
1
X. Y Z
0
1
0
1
X.YZ
0
1
1
0
1
0
0
1
1
0
1
0
1
1
0
1
1
1
1
0
The Boolean function F(X, Y, Z) is given as: F (X, Y, Z) = X Y Z
+
.*. The logic circuit is
XY Z
+XY Z
XY Z
XY Z
Some Common Applications of Logic Gates: During the course of discussion about various digital logic gates, we have mainly discussed about the design, property and operation of them. In this article we will look at various applications of logic gates. Their applications are determined mainly based upon their truth table i.e. their mode of operations. In the following discussion we will look at the applications of basic logic gates as well as many other normal logic gates as well.
Application of OR gate Wherever the occurrence of any one or more than one event is needed to be detected or some actions are to be taken after their occurrence, in all those cases OR gates can be used. It can be explained with an example. Suppose in an industrial plant if one or more than one parameter exceeds the safe value, some protective measure is needed to be done. In that case OR gate is used. We are going to show this with the help of a diagram.
Application of OR gate:
The above figure is a typical schematic diagram where an OR gate is used to detect exceed of temperature or pressure and produce command signal for the system to take required actions.
Application of AND gate: There are mainly two applications of AND gate as Enable gate and Inhibit gate. Enable gate means allowance of data through a channel and Inhibit gate is just the reverse of that process i.e. disallowance of data through a channel. We are going to show an enabling operation to understand it in an easier way. Suppose in the measurement of frequency of a pulsed waveform. For measurement of frequency a gating pulse of known frequency is sent to enable the passage of the waveform whose frequency is to be measured. The diagram below shows the arrangement of the above explained operation.
Application of AND gate
Application of Ex-OR/Ex-NOR gate This type of logic gates are used in generation of parity generation and checking units. The two diagrams below shows the even and odd parity generator circuits respectively for a four data.
Parity generation using Ex-OR/Ex-NOR gates
With the help of these gates parity check operation can be also performed. The diagrams below show even and odd parity check.
Parity check using Ex-OR and Ex-NOR gates
Figure (a) shows the parity check using Ex-OR gates and the figure (b) shows the parity check using Ex-NOR gates.
Application of NOT gate or Inverters NOT gates are also known as inverter because they invert the output given to them and show the reverse result. Now the CMOS inverters are commonly used to build square wave oscillators which are used for generating clock signals. The advantage of using these is they consume low power and their interfacing is very easy compared to other logic gates.
Square wave oscillator by using a ring configuration: The above figure shows the most fundamental circuit made of ring configuration to generate square wave oscillator. The frequency of this type generator is given by
Bibliography 1. Website
www.wikipedia.org
www.google.com
www.yahoo.com
2. BOOKS:
Comprehensive Practical Manual
Pradeep’s New Course Chemistry
Dinesh Companion Chemistry for Class 12
NCERT Class XII
