Answers for E.C.E 4

Below are the answers for questions asked in E.C.E 4

1. Speech amplifiers are mainly used as Class A amplifiers.
2. In a low level AM system, amplifier following the modulated stage must be a Linear Device.
3. Linearity
4. If the modulation index is more than 100% then modulated carrier signal will periodically reduced to zero. This will not effect the working of transmitter but the receiver will produce a distorted output.
5. Modulation is the process of converting one or more property of a high frequency Carrier wave according to the input signal. 
6. -
7. Class C
8. -
9. A linear amplifier
10. 0 to 1
11. 100 watts
12. With the help of formula of capacitance of parallel plates i.e. 

 

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Symbols of Different Transistors

There are mainly 2 families of Transistor i.e. Bipolar and Uni-polar Transistors.
Bipolar Transistors have 2 kind of carriers both holes and electrons while Unipolar Transistors 
have only single carrier either Hole or electrons.

Below are the symbols for BJT, FET, MOSFET, Duel gate MOSFET, Inductive channel MOSFET and Single connection Transistor.

fig a - BJT

fig b - FET

fig c - MOSFET

fig d - Duel gate MOSFET

fig e - Inductive Channel MOSFET

fig f - Single connection Transistor

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Network Theorems

Superposition Theorem

The response in any element of linear, bilateral network containing more than one source is the sum of the response produced by the sources each acting independently.
The superposition principle is only applicable to linear networks and systems.
The superposition theorem does not apply to the power as power is proportional to square of the current which is not a linear function.
Steps:-

1. Select a single source. Short the other voltage sources and open the current source, if internal impedance's are not known. If known than replace them by their internal impedance.
2. Find out the current through or the voltage across the required element, due to the source under consideration.
3. Repeat the above step for all the sources.
4. Add all the individual effect produced by individual sources to obtain the total current in or voltage across the element.

Thevenin's Theorem

Any combination of linear bilateral circuit elements and active sources, regardless of the connection and complexity, connected to a given load Z_L  may be replaced by a single two terminal network consisting of a

Single voltage source of V_TH and a single impedance Z_eq in the series with the voltage source, across the two terminals of the load Z_L.

Steps:-

1.       Remove the branch impedance, through which current is required to calculate.

2.       Calculate the voltage across the open circuited terminals. This voltage is Thevinin’s equivalent voltage V_TH .

3.       Calculate the equivalent impedance Z_eq as viewed through the two terminals of the branch from which current is to be calculated by removing that branch impedance and replacing all the independent sources by their internal impedance.

4.       The required current through the branch is given by, I = V_TH / Z_L + Z_eq .

Norton’s Theorem

Any combination of linear bilateral circuit elements and active services regardless of the connection or complexity, connected to a given load Z_L can be replaced by a simple two terminal network consisting of a single current source of I_N and a single impedance Z_eq in parallel with it, across the two terminals of the load Z_L .

Steps:-

1.       Short the branch through which the current is to be calculated.

2.       Find out the current through this short circuited branch. This current is nothing but the Norton’s current I_N.

3.       Calculate the equivalent impedance Z_eq as viewed through the two terminals of interest by removing the branch impedance and making all the independent sources inacticve.

4.       The current through the branch of interest is  I = I_N * Z_eq / Z_EQ + Z_L.

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Different Logic Gates

Logic gates are the general purpose electronics devices which have a specific o/p state for diffferent combinations of input.

Different types of Logic gates:-

1. AND Gate

 
Symbol 
 

Truth table     

INPUT		OUTPUT
A	B	A AND B
0	0	0
0	1	0
1	0	0
1	1	1

Relationship between inputs and output

Output = A and B
                  or
                A.B
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2. OR Gate


Symbol


Truth table

INPUT		OUTPUT
A	B	A OR B
0	0	0
0	1	1
1	0	1
1	1	1

Relationship between inputs and output

Output =    A or B

                    or

                  A+B

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3. NOT gate

Symbol

Truth Table

INPUT	OUTPUT
A	NOT A
0	1
1	0

Relationship between inputs and output

Output =  Not A

                    or

                    

=============================================================

4.NOR gate

Symbol

Truth Table

INPUT		OUTPUT
A	B	A NOR B
0	0	1
0	1	0
1	0	0
1	1	0

Relationship between inputs and output

Output = Not(A OR B)

                         or 

                    

===========================================================

5.NAND gate

Symbol

Truth table

INPUT		OUTPUT
A	B	A NAND B
0	0	1
0	1	1
1	0	1
1	1	0

Relationship between inputs and output

Output =  Not (A AND B)

                           or

                       

============================================================

6. XOR gate

Symbol

Truth Table

INPUT		OUTPUT
A	B	A XOR B
0	0	0
0	1	1
1	0	1
1	1	0

Relationship between inputs and output

Output  =   [ A AND (NOT B) ] OR [ (NOT A) AND B ]

                                                    or

                                              

==============================================================

7. XNOR gate

Symbol

Truth Table

INPUT		OUTPUT
A	B	A XNOR B
0	0	1
0	1	0
1	0	0
1	1	1

Relationship between inputs and output

Output = [ A AND B] OR [ (NOT A) AND (NOT B)]

                                     or

                       or 

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Terms in Linear Algebra

Some important terms related in Linear algebra

• Nul matrix A matrix in which all elements are zero is called Null matrix.
• Row matrix A matrix with 1 row and any no. of column is called Row matrix.
• Column matrix A matrix with 1 column and any no.of row is called column matrix
• Square matrix A matrix having equal no. of rows and columns is called Square matrix.
• Unit matrix A Square matrix in which all diagonol elements are 1 and all non diagonal elements are 0 is called Unit matrix.
• Diagonal Matrix A Square matrix in which all diagonal elements are non zero and non diagonal matrix are 0 is called Diagonal matrix.
• Scalar matrix A diagonal matrix with all diagonal elements are a scalar is called Scalar matrix.
• Symmetric Matrix A matrix which satisfy the relation ,,    a_ij = a_ji 
• _{Skew-symmetric matrix A matrix which satisfy the relationship ,,,} a_ij = -a_ji
• _{Triangular matrix A matrix whose elements below or above the leading diagonal are zero are called triangular matrix.}
• _{Transpose of a matrix A matrix obtained after exchanging the rows and columns of a matrix is called transpose of a matrix. It is donated as} A^T
• Orthogonal matrix A matrix which satisfy this relationship,,,,, A^T.A= 1
• Conjugate Matrix A matrix obtained by the complex conjugate of a matrix A is called Conjugate matrix. 

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Questions on electronics and communication engineering - 4

E.C.E 4

These questions depends upon the Topic 'Amplitude Modulation'

1. Speech amplifiers are usually operated as?
2. In a low level AM system, amplifiers following the modulated stage must be?
3. Low level modulating AM transmitter shows which property?
4. What happens when modulation index is more than 100% in AM?
5. What is the core function of a modulator?
6. Plot carrier transmission contains?
7. Which kind of modulation amplifiers are used in AM transmitter?
8. What is the main requirement for a long wave AM broadcast transmitter?
9. In a low level AM transmitter, the amplifier following the modulated state must be.
10. Modulation index lies between?
11. The power rating of a radio transmitter is around?
12. How we can determine the frequency of the piezoelectric effect?

E.C.E 1
E.C.E 2
E.C.E 3

Answers For E.C.E - 3

Answers of E.C.E - 3 Questions

1. Rhombic Antenna

2. Smaller the beam-width angle, higher the directivity.

3. There are more than one driven elements in a driven array.

4. The effective length of a antenna is always greater than it's physical length.

5. Earthmat is used to ensure: -

• Provision of earth from the antenna
• Improvement of radiation patteren
• impossibility of good ground connection

6.  2.15 db

7. The induced voltage will experience 2 maxima and 2 null.

8. as a UHF receiving antenna.

9. 2

10. We use counterpoise to reduce: -

• Rockiness of ground connection
• Difficulty of a good ground connection
• Provision of earth from antenna.

11.  Top loading can be done by increase effective height.

12. Input impedance of folded dipole antenna is 280 ohms.



13. Unipolar antenna is best for low frequency transmission.

14.An antenna behave as a resonant circuit, when it's length is a integral multiple of  ʎ/2

15. An half wave dipole produce Broadside pattern.

16. The range will increase by the factor of  2^1/2

17. 1/2r

18. Loop antenna is commonly used for direction finding.

   

19. A parabolic antenna is commonly used at 5000 MHz. 


20.  The radiation pattern of Parabolic antenna is highly directional.








Answer for E.C.E 3 Questions

E.C.E 1 Questions
E.C.E 2 Questions

Questions on electronics and communication engineering 3

E.C.E. Questions -3

The following questions depends upon Antenna and it's application

1. Give example of non-resonant antenna.
2. What is the Relationship between Beamwidth angle and Directivity?
3. Properties of a driven array.
4. Relationship between effective length and physical length.
5. Why we use a earthmat along with antenna?
6. The power gain of half wave array with respect to a isotropic radiater is?
7. When loop antenna is radiated through 360 degree, the induced voltage will experience?
8. The discone antenna can be used as a ?
9. The number of array in a simplest parasitic array is?
10. Why we use a counterpoise with the antenna?
11. Top loading of an antenna may be done by?
12. The input impedance of a folded dipole antenna is nearly?
13. Antenna normally preferred for low frequency transmission is?
14. An antenna behave as resonance circuit when?
15. What kind of pattern a half wave dipole Produced?
16. If the height of transmitter and receiver antennas are doubled, what will happen to the range of TV broadcast ?
17. How the electric field intensity of a Hertzian dipole at a remote point varies as?
18. What is the common use of loop antenna?
19. At what frequency a parabolic antenna is commonly used?
20. What is the radiation pattern of a parabolic antenna?

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Answers for E.C.E - 2

Answers of questions of   E.C.E 2

1. BAR, which is further equal to 100 kilopascles.

========================================

2. Due to the long term exposure to stress, metal deforms permanently, this phenomenon is          called creeping.

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3. Generally,  flux = flow rate / membrane area.

     It is measured by using Ballistic Galvanometer.

========================================

4. An ideal volt meter has infinite internal resistance. It acts as a open circuit.
    An ideal am meter has zero internal resistance. It acts as a short circuit.
========================================


5. Implantation defects(defects in substrate) causes the leakage current in transistor. It flows through the pn junction when it is inversely polarized.
    Another reason is TiSi gain, which occurs during annealing process.
========================================


6. Generally, the slope of load line depends upon Resistor value. 
========================================


7. Direct conversion ACD or  Flash ACD 
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8. 8
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Questions Based on Electronics and Communication Engineering - 2

Questions of E.C.E 2


These Topics have appeared in EIL(Electronics India Limited) Exam, October 2011

1. What is the use of pressure gauge?
2. Where the phenomenon of Creeping occur?
3. How to measure flux?
4. Property of a ideal meter.
5. Reason of Leakage current in transistor?
6. The slope of D.C. load line depends upon?
7. Which is the fastest A/D converter?
8. Min. no. of flip flops needed to measure a BCD decade counter is?
9. What are the Properties of negative logic system?
10. Examples of universal gates.
11. Properties of  a ideal current source.
12. Example of circularly polarized antenna.
13. Relationship between Directivity and Directive gain.
14. Define Broadcast array and give examples of Broadcast antennas.
15. Explain Lenz's law.
16. Explain Faraday law.
17. Unit of electric displacement current density.
18. Electric field strength at a given point is?
19. How we can generate PWM?
20. Disadvantage of F.M over A.M.
21. Use of de-amphasis circuit.
22. Quantization noise in PCM can be reduced by?
23. Millimeter wave has the range of?
24. Where we use pre-amphasis circuit?
25. Out of PCM, PAM, PPM and PWM, which one is highly immune to noise?

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Answer for E.C.E 1

Answers for  E.C.E  1  questions


   1.900-1800 Mhz

======================================

  2. CMRR measures the tendency of an Op-amp to reject the signal at input as their might be a small percentage of input signal is necessary. 


                                    

                                        CMRR = 20log₁₀  A_d/A_cm

          

                    A_{d =} differential gain

                    A_{cm =} common mode gain

======================================

3. Normal AM Broadcasting is done by Directional Antennas to reduce the change in broadcasting during day and night time.

=====================================

Questions based on Electronics and Communication Engineering

Questions of  E.C.E 1

1. The operating frequency of GSM in India.
2. CMRR of an Operational amplifier is?
3. Normal AM Broadcasting is done by?
4. In a lossless transmission line, the relationship between R,L,G, and C is?
5. Laplace transform of coswt?
6. Metal oxide varister is used for?
7. Diode made by metal and semiconductor?
8. What is Kernel?
9. What are the problems in TCP protocols?
10. Why we used polymorphism?
11. Fork( ) is used for?
12. RAID is used for?
13. Z inverse stands for?
14. Which junction is formed by Recrystallization?
15. How many GEO-Synchronous satellites cover the whole Globe?
16. Which antenna is used for TV broadcasting?
17. Area under unit impulse signal is?
18. What is De-Morgan Law?
19. What is the mode of wave propagation in free space?
20. In which type of amplifier current flows for less than half the cycle?

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