Fundamental of Electronics Engineering

Uttarakhand Technical University
B.tech (first year)

odd sem Examination, 2012,

Fundamental of Electronics

Engineering

time :- 3 hrs}

[Total Marks :100 ]

Note : Use of calculator is permitted. 

                                                              Section A

Q1:- Answer any 4 parts of the following :

 4*5=20

1. Explain intrinsic and extrinsic semiconductors by stating at least two examples of each.
2. Explain the basic concept of forbidden gap in semi conductors and discuss the effect of temperature on it.
3. Describe the formation of a p-n junction . Explain the depletion region and potential barrier.
4. Explain what do you understand by clipping circuit. Describe the working of the positive clipper.
5. Show that I_{E =}I_{B +} αI_{E +} I_{CBO .}   In what way  I_CBO  depend on temperature.
6. Explain the binary numbers . Taking 125.525 as an example, describe decimal to binary conversion.

Q2:- Attempt any four parts of the following :

4*5=20

1. Explain with the help of suitable diagram, how free electrons and holes contribute towards the electric current in a semiconductor.
2. Describe how n-type and p-type semi conductors are produced. State the main difference between them.
3. What do you understand by dc and ac resistance of a crystal diode. How will you find them using V-I characteristic.
4. Describe the various rating of Zener diode supplied by manufactures.
5. Calculate ac drain resistance , transconductance and amplification factor of a JFET with the help of following experimentally obtained data.V_{GS      0V                0V               -0.2V}
   V_{DS      7V                15V              15V}
   I_{D       10mA             10.25mA        9.65mA}
6. Draw the circuit of a practical single stage transistor amplifier. Explain the function of each     component.

Q3:- Attempt any two parts of the following :

2*10=20

1.  Describe half-wave rectifier and obtain an expression for the rectification efficiency of the half-wave rectifier is used to supply 12V dc to a resistive load R_L =500Ω. If the forward resistance of diode r_f  is 25Ω , find the rms value of ac voltage supplied to the circuit.
2. Explain the CB configuration of a transistor and draw its input and output characteristics.Describe      current amplification factor α collector current I_{C ,} input resistance r_i and output resistance r_o.
3. Draw the equivalent circuit of an ideal and actual zener diode. Explain V-I characteristics of a zener diode. Describe how it can be used as a shunt regulator.

Q4:- Attempt any two parts of the following :

2*10=20

1. Describe the construction and operating principle of JFET. State the advantage of JFET.  A JFET has a drain current of 5 mA . If  I_{DSS =} 10 mA and V_GS(OFF) = -6V,calculate the value of V_GS and pinch off voltage V_P.
2. Explain the need of transistor biasing circuit and state its essential requirements. Obtain the      expression for the stability factor S for CE configuration.
3. Draw an ac equivalent circuit of a single stage common emitter transistor amplifier and expression      for the voltage gain and power gain . An amplifier has an open circuit gain of 1000, an output resistance of 15Ω  and an input resistance of 7 KΩ  . It is supplied from a signal source of e.m.f 10 mV and internal resistance 3 KΩ . The amplifier feeds a load of 35Ω. Calculate the output voltage and power gain.

Q5:- Attempt any four parts of the following :

2*10=20

1.  What do you understand by an ideal operational amplifier ? Describe its characteristics and discuss lts limitations.In an op-amplifier ,the amplifier gain is 10000. The input series resistance feedback resistance are 100 KΩ and 500 KΩ respectively. If the input voltage is 1.0V, calculate output voltage. 
2. Describe NAND gate and NOR gate and discuss their characteristics. Explain why these are called as universal building blocks.
3. Describe the single variable theorem of Boolean algebra. With the help of truth tables, explain     associative and distributive laws.