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Test: The Transistor As an Amplifier & Transistor Construction - Electrical Engineering (EE) MCQ


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20 Questions MCQ Test - Test: The Transistor As an Amplifier & Transistor Construction

Test: The Transistor As an Amplifier & Transistor Construction for Electrical Engineering (EE) 2024 is part of Electrical Engineering (EE) preparation. The Test: The Transistor As an Amplifier & Transistor Construction questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: The Transistor As an Amplifier & Transistor Construction MCQs are made for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: The Transistor As an Amplifier & Transistor Construction below.
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Test: The Transistor As an Amplifier & Transistor Construction - Question 1

The emitter current consist of_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 1

The emitter current consists of two parts. It consists of hole current IpE constituted by holes. The other part is that it consists the electron current InE constituted by electrons.

Test: The Transistor As an Amplifier & Transistor Construction - Question 2

The total emitter current (IE) is given by_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 2

The total emitter current is the sum of InE and IpE. In commercial transistors, the doping of emitter region is made much heavier than base. Hence current by majority charge carriers InE is negligible when compared to current by minority charge carriers IpE.

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Test: The Transistor As an Amplifier & Transistor Construction - Question 3

A common base transistor amplifier has an input resistance of 20Ω and output resistance of 100kΩ. If a signal of 400mV is applied between emitter and base, find the voltage amplification. Assume αac to be one.

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 3

Clarification: IE = V/R=400M/20=20mA
IC=αIE= 1*20mA=20mA. VO=IC*RL=20m*1k=20V
Amplification, A= VO/signal voltage=20V/400m=50.

Test: The Transistor As an Amplifier & Transistor Construction - Question 4

The amplification factor for a transistor is given by_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 4

One of the most important application of a transistor is an amplifier. A small change in signal voltage produces an appreciable change in emitter current because the input circuit has low resistance (α=∆IC/IE).

Test: The Transistor As an Amplifier & Transistor Construction - Question 5

Why is the silicon mostly chosen when compared to germanium?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 5

The normal working temperature of germanium is approximately 70°C .The normal working temperature of silicon is approximately 150°C. The other advantages of using a silicon material are, it has a smaller ICBO and its variations are smaller with temperature.

Test: The Transistor As an Amplifier & Transistor Construction - Question 6

The change in output voltage across the load resistor for a transistor during amplification is_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 6

A small change of voltage ∆Vi between emitter and base causes a relatively large emitter current change ∆IE. We define by the symbol α that fraction of this current change which is collected and passes through RL.

Test: The Transistor As an Amplifier & Transistor Construction - Question 7

A transistor has an IC of 100mA and IB of 0.5mA. What is the value of αdc?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 7

Emitter current IE=IC+IB=100+0.5=100.5mA.
αdc=IC/IE=100/100.5=0.995.

Test: The Transistor As an Amplifier & Transistor Construction - Question 8

 A germanium transistor used as an amplifier has a collector cut off current ICBO=10µA at a temperature 27°C and β=50. What is the collector current when the base current is 0.25mA?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 8

 IC=βIB+(1+β)ICBO
IC=50*0.25/1000+51/100000=13.01mA.

Test: The Transistor As an Amplifier & Transistor Construction - Question 9

In a PNP germanium transistor, the cut in voltage is about_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 9

The cut in voltage of germanium is lower than that of silicon. If both germanium and silicon are in parallel, Ge starts conducting earlier and stops silicon from conducting.

Test: The Transistor As an Amplifier & Transistor Construction - Question 10

 In a PNP transistor operating in active region, the main stream of current is_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 10

The emitter-base junction is forward biased while collector-base junction is reversed biased. The transistor now operates in active region. Here, it can be used for amplification purpose.

Test: The Transistor As an Amplifier & Transistor Construction - Question 11

Which gas is used to fill the chamber in the grown junction type transistor construction?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 11

In the process of transistor construction, a crucible is placed in the chamber. This chamber consists of hydrogen or nitrogen. These gases help in the prevention of oxidation. It also contains purified Ge or Si at a temperature few degrees above its melting point.

Test: The Transistor As an Amplifier & Transistor Construction - Question 12

In a grown junction type construction, the method used form a junction transistor is_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 12

The grown junction may be formed by suddenly varying the rate of pulling the seed crystal from the melt. This method is based on the fact that proportion in which N and P type impurities crystallise i.e.., enter the grown crystal depends on the rate of pulling.

Test: The Transistor As an Amplifier & Transistor Construction - Question 13

Which of the following methods take impurity variation method for transistor construction?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 13

 In impurity variation method, the impurity content of the semiconductor is altered in its type as well as the quantity. For example, in making NPN germanium grown junction transistor, a small type of N type impurity is added to molten germanium and the crystal growth is started.

Test: The Transistor As an Amplifier & Transistor Construction - Question 14

Which of the following is true about grown junction type construction?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 14

This method is based on the fact that proportion in which N and P type impurities crystallise i.e.., enter the grown crystal depends on the rate of pulling. If the pulling rate is small, a P type crystal is grown. If the pulling rate is fast, an N type crystal is grown.

Test: The Transistor As an Amplifier & Transistor Construction - Question 15

What is the melting point of indium in alloy type transistors?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 15

This is similar to soldering and PNP transistor is generally is made by this process. In this method, first of all N type germanium is obtained. The N type wafer and indium dots are placed in a furnace and heated to about 500°C.

Test: The Transistor As an Amplifier & Transistor Construction - Question 16

The non rectifying base contact is made from_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 16

Leads for emitter and collector are soldered to the dots making non rectifying contacts. Further, non rectifying base contact is usually made from a welding a strip or loop of gold plated wire to the base plate.

Test: The Transistor As an Amplifier & Transistor Construction - Question 17

What is the thickness of wafer in the alloy type transistors?

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 17

The wafer of crystal has a 3-5m inch thickness and 80m inch square. This is placed in a graphite jig with a dot of prepared indium. One dot of an indium is 3 times larger than the other.

Test: The Transistor As an Amplifier & Transistor Construction - Question 18

The larger dot of the indium is used as_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 18

The wafer is placed in a graphite jig with a dot of prepared indium. One dot of an indium is 3 times larger than the other. Finally the larger dot is used as collector. The smaller dot is used as emitter.

Test: The Transistor As an Amplifier & Transistor Construction - Question 19

The electrical properties of a transistor in alloy type construction is determined by_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 19

Large area collector junction helps in collecting most of the holes emitted from the emitter ensuring that the collector current almost equals the emitter current. The spacing between two junctions inside germanium wafer is very small and determines the electrical properties.

Test: The Transistor As an Amplifier & Transistor Construction - Question 20

The grown junction type transistors is generally used for_________

Detailed Solution for Test: The Transistor As an Amplifier & Transistor Construction - Question 20

Grown junction type transistors are manufactured through growing single large crystal which is slowly pulled from the melt in crystal growing furnace. This is generally used for NPN transistors.

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