Electronics Circuit and Devices (EDC)

Viva Questions:

Q1) Distinguish between Intrinsic and extrinsic Semiconductor ?

Ans: Intrinsic Semiconductor: 1) These are the crystals of pure elements like germanium and silicon.
                                                  2) The number density of electrons is equal to the number density of                                                           holes.
                                                 3) The electrical conductivity is low.
                                                4) Electrical conductivity depends on temperature.

     Extrinsic Semiconductor: 1) Impurity are added.
                                                2) Number density of electrons are not equal to the density of holes.
                                               3) Electrical conductivity is high.
                                              4) Electrical conductivity depends on temperature as well as amount of                                                     impurity added. 

Q2) Define Hall Effect ?

Ans: Hall effect is the potential difference across a electrical conductor when a magnetic field is applied in a direction perpendicular to that of the flow of current.

Q3) Main Difference of unipolar and bipolar transistors ?

Ans: Bipolar transistors can have both minority and majority carriers flowing, whereas unipolar have only majority carriers. BJT transistor is Bipolar and MOSFET,JFET are unipolar. You can find mor elaborated detailed notes on BJT here.Switches in Electronics

Q4) Differentiate pinch off voltage and cut off voltage ?

Ans: Pinch of voltage: It is the minimum drain-source voltage at which the drain current essentially becomes constant.
        Cut off voltage: It is the gate source voltage where the channel completely cut off and the drain current becomes zero.

Q5) What is Tunnel Diode ?

Ans: Answer for this question is explained in this post. Diodes and its Application 
        Applications of tunnel diode are: High speed switching circuits and in logic circuits.

Q6) Difference between Avalanche Breakdown and Zener Breakdown ?

Ans:

Q7) In which region BJT acts as an Amplifier ?

Ans: In active region BJT acts as an amplifier.

Q8) Advantages of CE configuration over CB and CC ?

Ans:     CE                                        CB                                            CC
   
       Medium Rin                          Low Rin                                    High Rin
       High Rout                           High Rout                                 Low Rout
   High Voltage gain             High Volatge gain                    Voltage gain 0.99
  High Current gain              Current gain 0.99                  Medium current gain

Q9) Explain Early Effect ?

Ans: Early effect is the variation in the width of the base in BJT due to variation in applied base to collector voltage.

Q10) Advantage of Full wave Rectifier over Half wave Rectifier ?

Ans: 1) Full wave rectifier efficiency is double that of half wave.
        2) Ripple voltage is low and of higher frequency for full wave rectifier.
        3) Higher output voltage,higher output power and higher transformation utilization factor for                 full wave rectifier.
        4) No problem due to dc saturation of core.