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Test: Self Bias - Electrical Engineering (EE) MCQ


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10 Questions MCQ Test Analog and Digital Electronics - Test: Self Bias

Test: Self Bias for Electrical Engineering (EE) 2024 is part of Analog and Digital Electronics preparation. The Test: Self Bias questions and answers have been prepared according to the Electrical Engineering (EE) exam syllabus.The Test: Self Bias MCQs are made for Electrical Engineering (EE) 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Self Bias below.
Solutions of Test: Self Bias questions in English are available as part of our Analog and Digital Electronics for Electrical Engineering (EE) & Test: Self Bias solutions in Hindi for Analog and Digital Electronics course. Download more important topics, notes, lectures and mock test series for Electrical Engineering (EE) Exam by signing up for free. Attempt Test: Self Bias | 10 questions in 10 minutes | Mock test for Electrical Engineering (EE) preparation | Free important questions MCQ to study Analog and Digital Electronics for Electrical Engineering (EE) Exam | Download free PDF with solutions
Test: Self Bias - Question 1

The collector current (IC) that is obtained in a self biased transistor is_________

Detailed Solution for Test: Self Bias - Question 1

The collector current is analysed by the DC analysis of a transistor. It involves the DC equivalent circuit of a transistor. The base current is first found and the collector current is obtained from the relation, IC=IBβ.

Test: Self Bias - Question 2

The thermal runway is avoided in a self bias because_________

Detailed Solution for Test: Self Bias - Question 2

The self destruction of a transistor due to increase temperature is called thermal run away. It is avoided by the negative feedback produced by the emitter resistor in a self bias. The IC which is responsible for the damage is reduced by decreased output signal.

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Test: Self Bias - Question 3

What is the Thevenin’s voltage (VTH) in a self bias shown below?

Detailed Solution for Test: Self Bias - Question 3

The base current cannot be obtained directly from the KVL or KCL applications. The VCC and VBE cannot come under a single equation. So, the circuit is changed with a Thevenin’s voltage (VTH) and Thevenin’s resistance.

Test: Self Bias - Question 4

 What is the Thevenin’s resistance (RTH) in a self bias shown below?

Detailed Solution for Test: Self Bias - Question 4

The base current cannot be obtained directly from the KVL or KCL applications. A potential divider network is formed by R1 and R2.The VCC and VBE cannot come under a single equation. So, the circuit is changed with a Thevenin’s resistance.

Test: Self Bias - Question 5

The stability factor for a self biased transistor is_________

Detailed Solution for Test: Self Bias - Question 5

The stability of the circuit is inversely proportional to the stability factor. The emitter resistor is very large when compared to the Thevenin’s resistance. When β is not that large, then S=(1+ β)( RTH+ RE)/ (1+ β)RE+ RTH.

Test: Self Bias - Question 6

 In the circuit, the transistor has a large β value (VBE=0.7V). Find the current through RC.

Detailed Solution for Test: Self Bias - Question 6

We know, IC=VTH-VBE/RE
=9*3/9=3V. IC=3-0.7/2.3=1mA.

Test: Self Bias - Question 7

A silicon NPN transistor is used and it has a large value of β. Find the required value of R2when IC=1mA.​

Detailed Solution for Test: Self Bias - Question 7

 For silicon, VBE=0.8V, VCE=0.2V. IC=VTH-VBE/RE. By pitting the values, we have VTH=1.3V. R2 can be found from, VCCR2/R1+R2. We get R2=40KΩ.

Test: Self Bias - Question 8

The value of αac for all practical purposes, for commercial transistors range from_________

Detailed Solution for Test: Self Bias - Question 8

For all practical purposes, αac=αdc=α and practical values in commercial transistors range from 0.9-0.99. It is the measure of the quality of a transistor. Higher is the value of α, better is the transistor in the sense that collector current approaches the emitter current.

Test: Self Bias - Question 9

Which of the following is true?

Detailed Solution for Test: Self Bias - Question 9

HJ-C is thermal resistance between junction and case and HC-A is thermal resistance between case and ambient. The circuit designer has no control over HJ-C. So, a proper approach to dissipate heat from case to ambient is through heat sink.

Test: Self Bias - Question 10

Directions: Each of the next items consists of two statements, one labeled as the `Assertion (A)' and the other as 'Reason (R)' You are to examine these two statements carefully and select the answers to these items using the codes given below :

Assertion (A): The bias stability of a self-bias amplifier circuit can be improved by increasing the values of both the base resistor (RB) and the emitter resistor (RE).

Reason (R): The base resistor (RB) provides the required voltage to the base terminal and the emitter resistor (RE) provides negative feedback to the amplifier. 

Detailed Solution for Test: Self Bias - Question 10

The Self-bias circuit is also known as voltage divider bias.

The Self-bias circuit can be simplified by using the Thevenin theorem:

The stability factor for the self-bias circuit is:

So if RE increases or RB decreases,

then the circuit becomes more stable.

Hence the Assertion given is false.

The base resistance RB or RTH provides the required voltage to the base terminal and should be selected such that the emitter junction is forward biased.

Resistor RE results in negative feedback action which helps in keeping Ic stable,

Thus RE is responsible for stable Ic.

Hence, the Reason given is true.

So, option (d) is correct.

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