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DEPARTMENT OF MECHANICAL ENGG
ELECTRONICS AND MICROPROCESSOR
1. What are valence electrons?
Electron in the outer most shell of an atom is called valence electron.
2. What is forbidden energy gap?
The space between the valence and conduction band is said to be forbidden energy gap.
3. What are conductors? Give examples?
Conductors are materials in which the valence and conduction band overlap each other so there is a swift movement of electrons which leads to conduction. Ex. Copper, silver.
4. What are insulators? Give examples?
Insulators are materials in which the valence and conduction band are far away from each other. So no movement of free electrons and thus no conduction. Ex glass, plastic.
5. What are Semiconductors? Give examples?
The materials whose electrical property lies between those of conductors and insulators are known as Semiconductors. Ex germanium, silicon.
6. What are the types of Semiconductor?
1. Intrinsic semiconductor 2. Extrinsic semiconductor.
7. What is Intrinsic Semiconductor?
Pure form of semiconductors are said to be intrinsic semiconductor. Ex germanium, silicon.
8. What is Extrinsic Semiconductor?
If certain amount of impurity atom is added to intrinsic semiconductor the resulting semiconductor is Extrinsic or impure Semiconductor.
9. What are the types of Extrinsic Semiconductor?
1. P-type Semiconductor 2. N- Type Semiconductor.
10. What is P-type Semiconductor?
The Semiconductor which are obtained by introducing pentavalent impurity atom (phosphorous, antimony) are known as P-type Semiconductor.
11. What is N-type Semiconductor?
The Semiconductor which are obtained by introducing trivalent impurity atom (gallium, indium) are known as N-type Semiconductor.
12. What is doping?
Process of adding impurity to an semiconductor atom is doping. The impurity is called dopant.
13. Which is majority and minority carrier in N-type Semiconductor?
Majority carrier: electrons and minority carrier: holes.
14. Which is majority and minority carrier in P-type Semiconductor?
Majority carrier: holes and minority carrier: electrons.
15. What is depletion region in PN junction?
The diffusion of holes and electrons will result in difference in concentration across the junction which in turn results in the movement of the mobile charge
16. What is barrier voltage?
Because of the oppositely charged ions present on both sides of PN junction an electric potential is established across the junction even without any external voltage source which is termed as barrier potential.
17. What is meant by biasing a PN junction?
Connecting a PN junction to an external voltage source is biasing a PN junction. 18. What are the types of biasing a PN junction? 1. Forward bias 2. Reverse bias.
19. What is forward bias and reverse bias in a PN junction?
When positive of the supply is connected to P type and negative to N type then it is forward bias. When positive of the supply is connected to N type and negative to P type then it is reverse bias.
20. What is Reverse saturation current?
The current due to the minority carriers in reverse bias is said to be reverse saturation current.
21. What is reverse break down?
During reverse bias after certain reverse voltage the current through the junction increases abruptly thus breaking the crystal which is termed as reverse break down.
22. Give the diode current equation? I = I
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23. Give two applications of PN junction diode.
1. As rectifier in power supplies. 2. as switch in logic circuits
24. What is rectifier? Give its types.
Rectifier converts A.C to pulsating D.C. Types are HWR and FWR.
25. Explain N-type and P-type semiconductor with their energy band diagram? Maximum mark for this question: 8 marks
Definition of extrinsic semiconductor and its types (2 marks)
N-type semiconductor (3marks)
Definition Diagram of crystalline structure and energy band (2 marks)
P-type semiconductor (3marks)
Definition Diagram of crystalline structure and energy band (2 marks)
26. Explain the following a. Mobility b. Drift current c. Conductivity d. Diffusion current Maximum mark for this question: 12 marks a. mobility - definition and relation required (2 marks) b. Drift current – definition, diagrams and derivation of relation required (4marks) c. Conductivity - definition and relation required (2 marks) d. Diffusion current - definition, diagrams and derivation of relation required (4marks)
27. What is break down in diode? What are its types?
Maximum mark for this question: 6 marks Definition of break down and explanation (2 marks) Zener break down (2 marks)
Unit II TRANSISTORS
1. What is a transistor (BJT)?
Transistor is a three terminal device whose output current, voltage and /or power is controlled by input current.
2. What are the terminals present in a transistor?
Three terminals: emitter, base, collector.
3. What is FET? FET is abbreviated for field effect transistor.
It is a three terminal device with its output characteristics controlled by input voltage.
4. Why FET is called voltage controlled device?
The output characteristics of FET is controlled by its input voltage thus it is voltage controlled.
5. What are the two main types of FET?
1. JFET 2. MOSFET.
6. What are the terminals available in FET?
1. Drain 2. Source 3. Gate
7. What is JFET?
JFET- Junction field effect transistor.
8. What are the types of JFET?
N- channel JFET and P- Channel JFET
9. What are the two important characteristics of JFET?
1. Drain characteristics 2. Transfer characteristics.
10. What is transconductance in JFET?
It is the ratio of small change in drain current to he corresponding change in drain to source voltage.
11. What is amplification factor in JFET?
It is the ratio of small change in drain to source voltage to the corresponding change in Gate to source voltage.
12.Why do we choose q point at the center of the loadline?
The operating point of a transistor is kept fixed usually at the center of the active region in order that the input signal is well amplified. If the point is fixed in the saturation region or the cut off region the positive and negative half cycle gets clipped off respectively.
13. List out the different types of biasing. .
_ Voltage divider bias ,Base bias,Emitter feed back bias,Collector feedback bias,Emitter bias.
14. What do you meant by thermal runway?
Due to the self heating at the collector junction, the collector current rises. This causes damage to the device. This phenomenon is called thermal runway.
15. Why is the transistor called a current controlled device?
The output characteristics of the transistor depend on the input current. So the transistor is called a current controlled device.
16. Define current amplification factor?
It is defined as the ratio of change in output current to the change in input current at constant.
17. What are the requirements for biasing circuits?
The q point must be taken at the Centre of the active region of the output characteristics. Stabilize the collector current against the temperature variations. Make the q point independent of the transistor parameters. When the transistor is replaced, it must be of same type.
18. When does a transistor act as a switch?
The transistor acts as a switch when it is operated at either cutoff region or saturation region
19. What is biasing?
To use the transistor in any application it is necessary to provide sufficient voltage and current to operate the transistor. This is called biasing.
20. What is stability factor?
Stability factor is defined as the rate of change of collector current with respect to the rate of change of reverse saturation current.
21. Explain about the various regions in a transistor?
The three regions are active region saturation region cutoff region.
22. Explain about the characteristics of a transistor?
Input characteristics: it is drawn between input voltage & input current while keeping output voltage as constant. Output characteristics: It is drawn between the output voltage &output current while keeping input current as constant.
23. Explain the construction, operation, volt ampere characteristics, and application of SCR, also explain its two transistor model. Maximum mark for this question: 16 marks Construction (2marks) Equivalent circuit and two transistor model (2marks) Operation (4marks) Volt ampere characteristics (4marks) Application (2marks)
24. Explain the construction, operation, equivalent circuit, volt ampere characteristics, and application of UJT. Maximum mark for this question: 16 marks Construction (4marks) Equivalent circuit (2marks)
25. Explain the construction, operation, equivalent circuit, volt ampere
characteristics, and application of DIAC. Maximum mark for this question: 16 marks Construction (4marks) Equivalent circuit (2marks) Operation (4marks) Volt ampere characteristics (4marks) Application (2marks)
26. Explain the construction, operation, equivalent circuit, volt ampere characteristics, and application of TRIAC Maximum mark for this question: 16 marks Construction (4marks) Equivalent circuit (2marks) Operation (4marks) Volt ampere characteristics (4marks) Application (2marks)
Unit III DIGITAL ELECTRONICS
1. Define binary logic?
Binary logic consists of binary variables and logical operations. The variables are designated by the alphabets such as A, B, C, x, y, z, etc., with each variable having only two distinct values: 1 and 0. There are three basic logic operations: AND, OR, and NOT.
2. Convert (634)
to binary 634 = 110 011 100 Ans = 110011100
3. Convert 0.640625 decimal number to its octal equivalent. 0.640625 x 8 = 5.125 0.125 x 8 = 1.0 0.640 625 10 = (0.51)
4. Convert 0.1289062 decimal number to its hex equivalent 0.1289062 x 16 = 2.0625 0.0625 x 16 = 1.0 0.1289062 = (0.21)
5. Substract (0 1 0 1)
from (1 0 1 1)
2 1 0 1 0 0 1 0 1 Answer = 0 1 1 0
6. Add (1 0 1 0)
and (0 0 1 1)
2 1 0 1 0 0 0 1 1 Answer = (1 1 0 1)