government engineering college,dahod electrical …now superseded by the digital computer, op-amps...

GOVERNMENT ENGINEERING COLLEGE,DAHOD

ELECTRICAL ENGINEERING

SUBJECT CODE: 2110016

SUBJECT NAME: BASIC ELCTRONICS

BASIC ELCTRONICS 1

Experiment:

AIM: To Study Ideal Differentiator

Equipments Needed :

1. Analog board of AB82.

2. DC power supplies +12V, +15V from external source or ST2612 Analog Lab.

3. Digital multimeter.

4. 2 mm patch cords.

THEORY:

The Ideal Differentiator:

The ideal differentiator is shown in Figure.

The placement of the capacitor and resistor are reversed as compared to an integrator.

A differentiator produces an output that is proportional to the rate of change of the input

voltage.





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The Practical Differentiator: circuit:

Input output waveform:





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How Differentiator Works:

The relation between charge and current

But

The current is converted to a voltage,

For a sinusoidal input,

Output is given by,





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Result:

Conclusion:





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SECOND METHOD FOR OP-AMP AS DIFFERENTIATOR:

Appling Nodal analysis at node ,

( = 0 because input impedance of Op-Amp = )

C

C

( But )

C

C

C

C





BASIC ELCTRONICS 6

C

C

C

Experiment:

Aim: : To perform and measure the gain of Op-Amp based Inverting Amplifier circuit.

Components required:

Function generator, CRO, Regulated Power supply, resistor, capacitor, 741 IC, connecting wires.

Theory:

Introduction

The term operational amplifier or "op-amp" refers to a class of high-gain DC coupled amplifiers with

two inputs and a single output. The modern integrated circuit version is typed by the famous

741 op-amp. Some of the general characteristics of the IC version are:

o High gain, on the order of a million

o High input impedance, low output impedance

o Used with split supply, usually +/- 15V

o Used with feedback, with gain determined by the feedback network.

The operational amplifier (op-amp) was designed to perform mathematical operations. Although

now superseded by the digital computer, op-amps are a common feature of modern analog

lectronics. The op-amp is constructed from several transistor stages, which commonly include a

differential input stage, an intermediate-gain stage and a push-pull output stage.

The differential amplifier consists of a matched pair of bipolar transistors or FETs. The push-pull

amplifier transmits a large current to the load and hence has small output impedance.

The op-amp is a linear amplifier with Vout / Vin.

The DC open-loop voltage gain of a typical op-amp is 103 to 106. The gain is so large that most

often feedback is used to control the stability. The cheap models operate from DC to about 20 kHz,

while the high-performance models operate up to 50 MHz.





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A popular device is the 741 op-amp. It is usually available as an IC in an 8-pin dual, in-line package

(DIP).

Inverting Amplifier

Theory: The circuit diagram of An inverting-amplifier is as shown below in Fig2(a).The signal which

is to be amplified is applied to the inverting(-) terminal of an Op-Amp. The amplified output signal will

be 180o out of phase with the input signal. The output waveform is inverted as shown in Fig

2(b).Therefore this amplifier is known as “An inverting-amplifier” .

The An inverting-amplifier circuit is built by grounding the positive input of the operational amplifier

and connecting resistors R1 and R2, called the feedback networks, between the inverting input and the

signal source and amplifier output node, respectively.

Operation:

i) The signal to be amplified Vin has been connected to the inverting terminal via resistance R1.The

other resistor R2 ,connected between output and inverting terminal is called as “ Feedback” Resistor.

ii) The Non-inverting terminal is connected to the ground.

iii) As the Op-Amp is an ideal one its open loop voltage gain Av is equals to infinity and input

resistance Ri = infinity.

iv) The input and output waveform are shown in Fig 2(b).





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Fig:2(a)::Inverting Amplifier configuration of an op-amp

Fig:2(b)::input output waveform of an op-amp Inverting Amplifier configuration

Procedure:

1. Connect the circuit as shown in the circuit diagram.

2. Give the input signal as specified.

3. Switch on the power supply.

4. Note down the outputs from the CRO

5. Draw the necessary waveforms on the graph sheet.





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Observations:

1. Observe the output waveform from CRO. An inverted and amplified waveform will be observed.

2. Measure the input and output voltage from the input and output waveform in the CRO.

3. Calculate

4. Compare the theoretical voltage gain from the above equation with the

Experimental value obtained by dividing output voltage by input voltages observed.

5. Observe outputs of the inverting amplifier circuit using different input waveforms.

Calculations:

1. Calculate experimentally observed voltage gain Av using observed Vo& Vin from CRO.

2. Theoretically voltage gain is given by:

Result:

Hence the op-amp can configure as inverting amplifier circuit as observed from the output waveforms.

Op-Amp as an inverting configuration always gives output as an amplified inverted form of input

signal.

The gain of closed loop Op-Amp depends on R1 and R2.

Experiment:

Aim : To perform and measure the gain of Op-Amp based Non- Inverting Amplifier circuit.

THEORY :

The non-inverting amplifier using op-amp is as shown in fig.3 (a).

Here the signal which is to be amplified is applied to the non-inverting (+) terminal of Op-amp.

As shown in fig.3(b), the input output waveform are in phase with each other.





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The negative feedback is incorporated in this circuit via the feedback resistor R2 which is

connected between the output and inverting terminal of Op-amp.

The input signal is applied to the positive or non-inverting input terminal of the operational

amplifier, and a portion of the output signal is fed back to the negative input terminal.

Figure 3 (a): Non-inverting amplifier configuration of op-amp

Fig: 3 (b): input output waveform of an op-amp non-Inverting Amplifier configuration

Non-Inverting Amplifier Voltage Gain

The output is applied back to the inverting (-) input through the feedback circuit (closed loop) formed

by the input resistor R1 and the feedback resistor R2 . This creates �ve feedback as follows. Resistors

R1 and R2 form a voltage-divider circuit, which reduces Vo and connects the reduced voltage V2 to the

inverting input. The feedback is expressed as





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The difference of the input voltage, Vin and the feedback voltage, V2 is the differential input of the op-

amp. This differential voltage is amplified by the gain of the op-amp and produces an output voltage

expressed as

The closed-loop gain of the non-inverting amplifier is, thus

Result:

Hence the op-amp can configure as inverting amplifier circuit as observed from the output waveforms.

Op-Amp as non-inverting configuration always gives output as an amplified (in phase) version of input

signal.

The closed loop control gain is always greater than 1 for non-inverting configuration.

We notice that the closed loop gain is independent of open-loop gain of op-amp.

Experiment:

AIM: To study and verify the Truth tables of D-FLIP-Flop.

APPARATUS:

Digital IC trainer kit

Patch cords

THEORY:

The flip flop is a bistable device, i.e., a circuit with only two stable states. A flip-flop circuit can

remember or store in binary bit (1 or 0) because of its bi-stable nature. The flip-flop responds to inputs.

If an input causes it to go to its ‘1’ state, it will remain there and “remember” a ‘1’ until some signal

causes it to go to ‘0’ state. Similarly, once placed in the 0 state, it will remain there until told to go to





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the ‘1’state. This simple characteristic, the ability of flip-flop to remain its state, makes it the basic

memory elements in the digital systems.

The D flip-flop:

Some dedicated application in digital electronics may not require the use of all states available in SR or

JK flip-flop that satisfies only the middle four rows of the JK flip-flop truth table is used extensively in

sequential building blocks like registers etc. This is called delay (or D) flip-flop. The input at D, at the

instant ‘t’ will appear at the output Q during instant ‘t+’,i.e., the D flip-flop gives delay to the input

signal.

Block diagram of D-Flip Flop:

Circuit diagram of D Flip-flop:

Truth Table of D Flip – flop:

INPUTS OUTPUTS





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0 0 1

0 1 0

1 0 1

1 1 0

PROCEDURE:

1. Connect the circuit as shown in fig.(A NOT gate is connected between the J & K inputs and the

D input is applied to the J input)

2. put both Pr and Cr ‘HIGH’ and verify the truth table

The Clocked D flip-flop:

The flip-flops are usually parts of a large digital sequential system. If both the inputs to the flip-flop do

not appear at the same instants of time, the output will be unstable till the input stabilizes. This is

sufficient, however to cause errors, which are transmitted sequentially resulting in cumulative error.

Hence, it is necessary that the state changes take place only during fixed intervals of time, determined

by some carefully regulated pulse train or discrete inputs. These inputs are different from the S-R

inputs. This additional input is called ‘CLOCK’ and the various elements in the system work in co-

ordination with it. Fig is the block diagram of clock D flip-flop. Output changes takes place only when

the clock pulse (or the level) appears.





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Block diagram of Clocked D-Flip Flop:

Circuit diagram of Clocked D Flip-flop:

Truth Table of Clocked D Flip – flop

INPUTS

OUTPUTS

Before clock

pulse After clock pulse

CLK

0 X X

1 0 X 0 1





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1 1 X 1 0

PROCEDURE:

1. Connect the circuits as shown in fig.

2. Use logic inputs switches for the flip-flop input and use a pulsar switch for the clock inputs

3. Verify the truth table.

CONCLUSION:_____________________________________________________________________

___________________________________________________________________________________

___________________________________________________________________________________

___________________________________________________________________________





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Experiment:

Aim : Perform AM Modulation using Scilab

Definition: In amplitude modulation amplitude of high frequency carrier is varied in accordance with

instantaneous amplitude of modulating signal.

Information signal or message signal or modulating signal

High frequency carrier wave

Modulated signal (Amplitude modulated signal)





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Equation of AM Modulation:

To simplify mathematical treatment, we will consider sinusoidal modulating signal. Let consider that carrier

wave and modulating signal are represented by following formulas.

Modulating signal: =

Carrier signal: =

Carrier frequency is higher than modulating signal or message signal frequency .

Amplitude modulated wave can be represented by following formula:

e = A ; Where, A = envelope of the modulated signal.

= ( + )

= ( + )

= .

Definition of modulation index:

In amplitude modulation index m is defined as the ratio of peak amplitude of modulating signal E m to

peak amplitude of carrier signal .

If peak amplitude of modulating signal is less than peak amplitude of carrier signal then modulation index

is less than I and no distortion occurs in the modulation single.

If peck amplitude of the modulating signal is greater than peak amplitude of the carrier signal then it is

called over modulation index greater than 1.

In this case, distortion occurs in the modulating signal.

Mathematically modulation index can be represented as:

Modulation index m =

To measure modulation Index, two methods are used one is waveform method and second is trapezoidal

method.





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Wave form method:

In wave form method, and measured directly from the wave form and modulation index is calculated

using above formulas.

An AM waves corresponding to m = 0, m = 1 and m > 1 is shown below in figure:

We can easily identify distortions in AM signal by looking at the pattern.

If there is a distortion the edge of trapezoidal are not linear but curvature.

Over modulation is also easily observed by horizontal line in the left.





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Program for AM Modulation:

clc;

fm=50;

fc=500;

Em=5;

Ec=5;

t=0:0.0001:0.1;

t1=0:0.01:1;

Vm=Em*sin(2*%pi*fm*t);

Vc=Ec*sin(2*%pi*fc*t);

x= Ec * sin(2*%pi*fc*t) + Em .* sin(2*%pi*fm*t).*sin(2*%pi*fc*t);

subplot(3,1,1);

plot(t,Vm);

title("Modulating signal")

subplot(3,1,2)

plot(t,Vc);

title("Carrier signal")

subplot(3,1,3)

plot(t,x);

title("Amplitude Modulated signal");





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Note:Change the value of Em to change the modulation index and get the waveforms for over

and under modulation.

Conclusion: Thus we have observed that amplitude of the carrier changes according to modulating

signal(information) in AM modulation and observed the waveform in scilab. Also Modulation index is

key parameter to decide the nature of modulation .





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EXPERIMENT

AIM: Study the principle and operation of a basic open loop and closed loop Control Systems.

APPARATUS:

(1) Trainer Kit for Open Loop Control system

(2) Trainer kit for Close Loop Control System

(3) Multimeter (4) Test Signal Generator

THEORY:

OPEN LOOP CONTROL SYSTEM:

Open loop control system is a non-feedback type control system wherein output is neither

measured nor compared with the reference input. For each reference input a fixed operating condition

exists. As there is no feedback taken, the open loop control system is unable to overcome any variation

in desired output due to internal or external disturbances.

In the trainer kit for study of open loop control system, the process is of charging of capacitor

using a constant current source. The reference input is the value of voltage to which the capacitor has to

charge. This reference input (value of voltage) can be adjusted by input command adjustment

potentiometer. The output of the system is the value of voltage up to, which the capacitor is charged.

Disturbance is generated by variation of constant current.

CLOSE LOOP CONTROL SYSTEM:

Close loop Control system is a feedback type of control system wherein the information about

instantaneous state of the output is fed back to input and is continuously compared with the reference

input. Depending on the difference between the actual output and desired output (which is indicated by

reference input signal) an error signal is generated that is fed to the control element so as to bring the

output of the system to desired value. If because of internal or external disturbance, the output of the

system deviates from its desired value because of feedback mechanism, the system can self correct and

hence works more efficiently and accurately as compared to the Open loop Control System.

In the trainer kit for the study of Close Loop Control System the process remains same i.e.

Charging of Capacitor using constant current source. The reference input is again variable voltage

which indicates voltage to which capacitor has to charge. Disturbance is provided by the variation of

current source. However, because of presence of feedback in this system compared to trainer for Open

loop Control System, the capacitor would charge to desired value set by reference input in spite of

change in value of current source.





BASIC ELCTRONICS 22

PROCEDURE:

(A) OPEN LOOP:

1. Keep the ‘Input Command Adj’ potentiometer on first mark on dial.

2. Keep the ‘disturbance Adj’ potentiometer fully anticlockwise position for minimum

disturbance current.

3. Connect 0-100 A at position marked ‘MA’.

4. Connect 0-50V DVM across the control output terminal.


6. Press the ‘Start Process’ push button. Process LED will glow.

7. Measure disturbance current and record its value. (Imin = ……………………..)

8. As soon as the process LED is ‘OFF’, measure and record the controlled output voltage.

Controlled voltage = ……………………. (Min disturbance)

9. Now keep the disturbance Adj potentiometer in max position. That is max disturbance.

10. Press the discharge push button the controlled output voltage will be zero.

11. Now press start process push button. Process LED will be ‘ON’.

12. Repeat 7 for the Imax………………………..

13. Repeat the above steps for the other settings of Input Command Adj potentiometer.

(B) CLOSED LOOP:

1. Connect 0-50 mA meter and DVM at appropriate terminals.

2. Keep the ‘disturbance Adj’ potentiometer fully anticlockwise position for minimum

disturbance current.


4. Keep the switch in discharge mode.

5. Set the switch in ‘RESTART’ mode.

6. Connect the digital voltmeter at the output terminals. The output voltage will increase but the

error signal will decrease, measure error voltage at Error signal Terminal.

7. As soon as Error signal becomes zero output will be 1 VDC. The process LED will be

ON/OFF. As it will try to maintain output voltage constant at 1 VDC.

8. Take Observation at different setting of input command signals.

EXPRIMENT:

Aim: To obtain the Cascade, Parallel and Feedback function using scilab.

Introduction:

Transfer Function: Transfer function is defined as a Laplace transform of output(response)of the

system to Laplace transform of input.





BASIC ELCTRONICS 23

G(s)=

Pictorial representation of functions performed by each component of a system and that of flow of

signals.

Components for Control system:

Terminology:





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• G (s ) ≡Direct transfer function = Forward transfer function.

• H (s ) ≡Feedback transfer function.

• G (s )H (s ) ≡ Open‐loop transfer function.

• C (s ) R (s ) ≡ Closed‐loop transfer function = Control ratio

• C (s ) E (s ) ≡ Feed‐forward transfer function.

1. Plant: A physical object to be controlled. The Plant G (s ) , is the controlled system, of which a

particular quantity or condition is to be controlled.

2. Feedback Control System (Closed‐loop Control System): A system which compares output to

some reference input and keeps output as close as possible to this reference.

3. Open‐loop Control System: Output of the system is not feedback to the system.

4. Control Element: G1(s ) is, also called the controller, are the components required to generate the

appropriate control signal M (s ) applied to the plant.

5. Feedback Element: H (s ) is the component required to establish the functional relationship between

the primary feedback signal B (s ) and the controlled output C(s)).

6. Reference Input :R (s ) is an external signal applied to a feedback control system in order to

command a specified action of the plant. It often represents ideal plant output behavior.

7. The Controlled Output C (s ) is that quantity or condition of the plant which is controlled.





BASIC ELCTRONICS 25

8. Actuating Signal E (s ) , also called the error or control action, is the algebraic sum consisting of the

reference input R (s ) plus or minus (usually minus) the primary feedback B (s ) .

9. Manipulated Variable :M (s ) (control signal) is that quantity or condition which the control

elements G1 (s ) apply to the plant G 2(s ) .

10. Disturbance U (s ) is an undesired input signal which affects the value of the controlled output C (s

). It may enter the plant by summation with M (s ) , or via an intermediate point, as shown in the block

diagram of the figure above.

11. Forward Path is the transmission path from the actuating signal E (s ) to the output C (s ).

12. Feedback Path is the transmission path from the output C (s ) to the feedback signal B (s ).

13. Summing Point: A circle with a cross is the symbol that indicates a summing point. The (+) or (−)

sign at each arrowhead indicates whether that signal is to be added or subtracted.

14. Branch Point: A branch point is a point from which the signal from a block goes concurrently to

other blocks or summing points.

BLOCK DIAGRAMS AND THEIR SIMPLIFICATION:

i) Cascade (Series) Connections:

In Cascade Connection the overall transfer function is calculated as the product of the all the

transfer function in series.





BASIC ELCTRONICS 26

ii) Parallel Connections

In parallel conncetion the overall transfer function is calculated as the addition or subtraction of

the TF depending on the connection with the summing point

iii)Feedback connection:





BASIC ELCTRONICS 27

The term feedback is used to refer to a situation in which two (or more) dynamical systems are

connected together such that each system influences the other and their dynamics are thus strongly

coupled. By dynamical system, we refer to a system whose behaviour changes over time, often in

response to external stimulation or forcing.

A) Program to find the overall transfer function for TF connected in Cascade :

function [out]=series(sys1, sys2)

out=sys1*sys2;

endfunction

exec series.sce;

s=%s ;

sys1=syslin ('c',( s+3) /( s+1));

sys2=syslin ('c',0.2/( s+2));

sys3=syslin ('c',50/( s+4));

sys4=syslin ('c',10/( s ));

a=series(sys1,sys2);

b=series(a,sys3);

y=series(b,sys4);

y=simp( y ) ;

disp (y , "C( s ) /R( s )=" )

OUTPUT:

C( s ) /R( s )=

300 + 100s

----------------

8s + 14s2 + 7s

3 + s

4





BASIC ELCTRONICS 28

B) Program to find the Overall Transfer function for all TF in Parallel:

function [out]=parallel(sys1, sys2)

out=sys1+sys2;

endfunction

exec parallel.sce;

s=%s ;

sys1=syslin ('c',( s+3) /( s+1));

sys2=syslin ('c',0.2/( s+2));

sys3=syslin ('c',50/( s+4));

sys4=syslin ('c',10/( s ));

a=parallel(sys1,sys2);

b=parallel(a,sys3);

y=parallel(b,sys4);

y=simp( y ) ;

disp (y , "C( s ) /R( s )=" )

OUTPUT:

C( s ) /R( s )=

80 + 264.8s + 247s2 + 69.2s

3 + s

4

------------------------------ ---------------

8s + 14s2 + 7s

3 + s

4





BASIC ELCTRONICS 29

C) Program to find the Transfer function for Feedback:

function [out]=series(sys1, sys2)

out=sys1*sys2;

endfunction

exec series.sce ;

s=%s ;

sys1=syslin ('c',3/( s*(s+1)));

sys2=syslin ('c', (s^2)/(3*( s+1)));

sys3=syslin ('c',6/(s));

a=(-1)*sys3 ;

b=series( sys1,sys2 ) ;

y=b/.a // f e e d b a c k o p e r a t i o n

y=simp( y )

disp (y , "C( s ) /R( s )=" )

OUTPUT:

C( s ) /R( s )=

3s

------------

- 15 + 6s + 3s2





BASIC ELCTRONICS 30

government engineering college,dahod electrical …now superseded by the digital computer, op-amps...

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