EE 2203 Electronic Devices and Circuits (EDC)Anna University Important Questions 2 marks and 16 marks questions | EE2203 important questions from all 5 units for 3rd semester EEE dpt (Syllabus included) ...

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EE 2203 Electronic Devices and Circuits (EDC)Anna University Important Questions 2 marks and 16 marks questions | EE2203 important questions from all 5 units for 3rd semester EEE dpt (Syllabus included) ... 

Posted by R.Anirudhan 

**we will update the important questions and topics soon ..here we have listed the repeated questions asked in AU question Papers**                           

EE2033 ELECTRONIC DEVICES AND CIRCUITS                               
                                      
1. PN DIODE AND ITS APPLICATIONS
PH junction diode-VI characteristics  â€" Rd, temperature effects  â€" Drift ad diffusion 
currents  â€" switching  â€" Rectifiers: HWR, FWR, BR, filters-Zener diode  â€" VI 
characteristics, Regulators (series and shunt), LED, LCD characteristics and applications.
2. BJT AND ITS APPLICATIONS
Junction transistor â€" Transistor construction â€" Input and output characteristics â€" CE, CB 
and CC configurations  â€" hybrid model  â€" Analytical expressions  â€" switching  â€" RF 
application â€" Power transistors â€" Opto couplers.
3. FET AN D ITS APPLICATIONS
FET â€" VI characteristics, VP, JFET â€" small signal model â€" LF and HF equivalent circuits 
â€" CS and CD amplifiers  â€"cascade and cascade  â€" Darlington connection  â€" MOSFET  â€"
Characteristics â€" enhancement and depletion
4. AMPLIFIERS AND OSCILLATORS
Differential amplifiers: CM and DM â€" condition for ofc-feedback amplifiers â€" stability â€"
Voltage / current, series / shunt feedback â€" oscillators â€" LC, RC, crystal
5. PULSE CIRCUITS
RC wave shaping circuits  â€" Diode clampers and clippers  â€" Multivibrators  â€" Schmitt 
triggers â€" UJT based saw tooth oscillators.


UNIT-I - PN DIODE AND ITS APPLICATIONS
1. What is depletion region in PN junction?
The region around the junction from which the mobile charge carriers (electrons 
and holes) are depleted is called as depletion region. Since this region has immobile ions, 
which are electrically charged, the depletion region is also known as space charge region.
2. Give the other names of depletion region?
i. space charge region
ii. Transition region
3. What is barrier potential?
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.
4. What is meant by biasing a PN junction?
Connecting a PN junction to an external voltage source is biasing a PN junction.
5. What are the types of biasing a PN junction?
1. Forward bias 2. Reverse bias.
6. What is forward bias and reverse bias in a PN junction?
When positive terminal of the external supply is connected to P region and 
negative terminal to N region, the PN junction is said to be forward biased. Under 
forward biased condition the PN region offers a very low resistance and a large amount 
of current flows through it.
7. What is reverse bias in a PN junction?
When positive terminal of the external supply is connected to N type and negative 
terminal to P type then the PN junction is said to be in reverse bias. Under reverse biased 
condition the PN region offers a very high resistance and a small amount of current flows 
through it.
8. What is Reverse saturation current?
The current due to the minority carriers  in reverse bias is said to be reverse 
saturation current. This current is independent of the value of the reverse bias voltage.
9. Why contact differences of potential exist in PN junction?
When a PN junction is formed by placing a p-type and n-type material in intimate 
contact, the Fermi level throughout the newly formed specimen is not constant at 
equilibrium. There will be transfer of electron and energy until Fermi levels in the two 
sides did line up. But the valence and conduction band in p side cannot be at the same 
level as in n side .this shift in energy level results in contact difference of potential.
10. What is the static resistance of a diode?
Static resistance R of a diode can be defined as the ratio of voltage V across the 
diode to the current flowing through the diode .
R = V/ I
Where
R - Static resistance of a diode
V - Voltage across the diode
I - current across the diode
11. Define dynamic resistance.
Dynamic resistance of a diode can be defined as the ratio of change in voltage 
across the diode to the change in current through the diode.
r = V / I
Where
r - Dynamic resistance of a diode
V - change in voltage across the diode
I - change in current through the diode
12. What is an amplifier?
An amplifier is a device which produces a large electrical output of similar
Characteristics to that of the input parameters.
13. Why do we choose q point at the center of the load line?
The operating point of a transistor is kep t 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.
14. 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.
15. 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.
16. What is operating point?
For the proper operation of the transistor a fixed level of current and voltages are 
required. This values of currents and voltages defined at a point at which the transistor 
operate is called operating point.
12.   Define luminescence
Light can be emitted by a solid when it is stimulated by the source of incident 
energy. This phenomenon is called luminescence
13.  What are the types of luminescence?
                  
a) Photoluminescence b) Electroluminescence
14.     Define photoluminescence
                
It is incident energy is in the form of photons, then it is called  
photoluminescence
15.    Define electroluminescence
                
If the radiation is produced by the application of an electric field, it is termed as 
electroluminescence
16.  Which colour of light is emitted by GaAs, Gp, GaAsp
                   
GaAs - Infra red radiation (invisible)  GaP - Red or Green
                   GaAsP - Red or Yellow   
17. Define injection laser diode
        
When the emitted light is coherent, (ie) essentially   monochromatic, then such a 
diode is referred to as an injection laser diode
  18.  What are the limitations of LCD?
       
* It requires an external or internal light source 
            * Temperature range is limited to about 60oC 
* Lime time is limited due to chemical degeneration
19.  What are the two types of LCDs?
     
a) Dynamic scattering type LCD b) Field effect LCD
20.   Name the crystal materials used to LCD?
      
a) Nematic b) Cholesteric

PART-B
1. Explain forward bias and reverse bias in a PN junction and also VI characteristics of 
PN junction.
2. Explain the VI characteristics of zener diode.
3. Explain the characteristics of LED and LCD.
4. How does the zener diode act as a voltage regulator? Explain.
5. Explain the hall wave and full wave rectifiers with relevant diagram.


UNIT â€" II - BJT AND ITS APPLICATIONS
1. Define Transistor
    Transistor consists of two junctions formed by sandwiching either P-type or Ntype semiconductor between a pair of opposite types.
2. Write the current amplification factor for a CB transistor.
           a = Change in Collector Current at constant VCB / Change in emitter current
3.  Write the formula for input resistance in a CB transistor
     Input resistance = Change in base - emitter voltage / Change in emitter current at 
constant VCB
4.  Write the current amplification factor for a CE transistor.
b = Change in Collector Current / Change in base current at constant VCE
5 . Define transistor action.
          A transistor consists of 2 coupled PN junctions. The base is a common region to 
both junctions and makes a coupling between them. Since the base regions are smaller, a 
significant interaction between junctions will be available. This is called
transistor actions.
6.  Define delay time
      It is defined as the time required for the current to rise from 0 to 10% of its 
maximum value.
7. Define rise time
It is the time required for the current to rise from 0 to 90 percentage of the 
maximum value.
8. Define turn-on time 
          
It is the time required for the current to rise from 0 to 90 percentage of the 
maximum value  ton = td + tr
9. Define fall time 
       
It is the time required for the Collector current to fall from 90 to 10 percentages of  
Ics.
10. Define Storage time
      
It is the time required to fall from 100 to 90 percent of Ics.
11. Define turn-off time 
    
It is the time required to fall from 100 to 90 perc ent of Ics.  Toff=ts+tr
12.Define hybrid parameters.
        
Any linear circuit having input and output terminals can be analysed by four 
parameters(one measured on ohm, one in mho and two dimensionless) called hybrid or hparameters.
13. What are the use of h - Parameters?
        
It perfectly isolates the input and output circuits. Its source and load currents are 
taken into account.
14. . Define power transistors  
         
Power transistors are those which handle a large amount of current and also 
dissipates large amount of power across collector base junction.
15. Define current amplification factor in CC transistor.
        
g =Change in emitter current /Change in base curre nt at constant VCE
16.   Which is the most commonly used transistor configuration?Why?
       The CE Configuration is most commonly used. 
The reasons are
* High Current gain
* High voltage gain 
* High power 
* Moderate input to output ratio.
17. What are the values of input resistance in CB, CE & CC Configuration
      
CB - Low about 75 CE - Medium About 750 CC - Very high about 750.
18.   Write the voltage and current equation for hybrid parameters.
             V1 = h11i1 + h12V2 i2 = h21i1 + h22V2
19.   What are the values of h-parameters?
         
  h11 = V1/ i1 ; h12 = V1 / v2 ; h21 = i2 / i1 ; h22 = i2 / v2
20.  h â€" parameter is applied to linear ci rcuit : True or False.
True

PART-B
   1. a). Explain the operation of PNP & NPN transistor? (12)
      b). What is transistor? State its types (4)
    2. a). Explain the current components of a transistor? (8)
        b). Explain the transistor switching time? (8)
    3. a). Explain Ebers â€" Moll model . (8)
        b). Compare CE â€" CB â€" CC Configuration? (8)
   4. a). Explain the input & output characteristics of CE  configuration of  a                 
transistor? (12)
b). State FET& its types? (4)
    5. a)Explain the input & output Characteristic of CB configuration of a  transistor? (12)
          b) State about the VMOS Devies?

UNIT   - III - FET AND ITS APPLICATIONS
1. What are the advantages of FET

            * Input impedance is very high. This allow high degree of  
       Isolation between the input & output Circuit.
*Current carriers are not crossing the junctions hence noise is   
                   highly reduced.
             * It has a negative temperature Co-efficient of resistance. This 
                  avoids the thermal runaway.
2.  What are the advantages of MOSFET compared to JFET?
                         
The input impedance of MOSFET is higher than that of JFET
3.   What are the two modes of MOSFET?
                         (a) Depletio n mode (b) Enhancement mode
4.  Why UJT is called so?
             UJT has only one PN junction so it is called as uni junction transistor
5. What are the advantages of SCR and TRIAC?
              
SCR performs rectification, inversion and regulation of power flow    
     TRIAC is a bidirectional switch and hence it can conduct in both the direction.
6. Define breakdown voltage
                 The applied voltage at which the thyristors conducts heavily without  gate 
voltage.
7. Define latching current
                          It is the minimum current required to latch the device from OFF to  ON 
state
8. Define holding current
       It is defined as the minimum current required to hold the device into  
conduction.
9.  Define turn - on time
         It is the time taken by the SCR to reach to its full conduction from the time the 
trigger is applied.
10.  Define turn - off time

     It is the finite time taken by the SCR after application of the reverse voltage to 
switch the device off.
11.  What are the advantage of SCR?
         Switching speed is high No moving parts. So it gives noiseless operation at high 
frequency It controls large current in the load by means of small gate current Occupies 
less space
12.  Give some applications of thyristor?
          Used for power control Used for speed control of a d.c shunt motor
13.  Define finger voltage
         It is defined as the minimum voltage which is required between anode and the 
cathode of thyristor to trigger into conduction
14.   What is the name for solid state equivalent of thyristor
Thyratron.
15. Define inter-base resistance 
        It is the resistnce offered by the silicon bar
16.  Define pinch-off voltage
      It is the drain source voltge above which the drain current becomes constant
17.  What are the differences between JFET & BJT
S.NO             JFET                 BJT
1. Unipolar device                 Bipolar device
2. High input impedance         Low input impedance due to forward bias
3. Voltage driven device        Current driven device
4. Gain is characterized by 
transconductance  gain  
                                               Gain is characterized by voltge
5. Low noise level                  High noise level
18.  What is amplification factor
 It is the product of drain résistance and transconductance m=Rd x gm Rd=Drain
resistance, gm=Transconductance
19.  Define drain resistance 
          It is the ratio of change in drain source voltage to change in drain current at 
constant gate source voltage.
20. What is Reverse saturation current?
The  current  due  to the  minority  carriers  in  reverse  bias  is  said to  be  reverse  
saturation  current. This current is independent of the value of the reverse bias voltage. 

   PART-B
1. Compare the following
a) D MOSFET & EMOSFET
b) n-channel MOSFET & p â€"channel MOSFET. (16)
2. a). What are the applications of JFET? Explain JFET as VVR. (8)
    b). Explain the biasing technique for enhancement MOSFET? (8)
3. Prove that the voltage divider biasing provide better stability than other techniques? 
(16)
UNIT â€" IV - AMPLIFIERS AND OSCILLATORS

1. What is an amplifier?
An amplifier  is  a  device  which produces  a  large  electrical  output  of  similar
Characteristics to that of the input parameters.
2. Why do we choose q point at the center of the load line?
The operating point of a tra nsistor is kept fixed usually at the center of the active 
regionin 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.
3. 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.
4. 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.
5. What is operating point?
For  the  proper  operation  of  the  transistor  a  fixed level  of  current and 
voltages  are  required. This  values  of  currents  and voltages  defined at  a  point  at  
which  the  transistor operate is called operating point.
6. What is d.c load line?
The d.c load line is defined as a line on the output characteristics of the transistor 
which gives the value of Ic & VCE corresponding to zero signal condition.
7. What is the necessary of the coupling capacitor?
It is used to block the DC signal to the transistor amplifier. It allows a c & blocks 
the d c.
8. Why is the operating point selected at the Centre of the active region?
The  operating  point  is  selected  at  the  Centre  of  the  active  region  to get  to 
perfect amplification. Moreover there is no distortion.
9. Define an operational amplifier.
An operational amplifier is a d irect-coupled, high gain amplifier consisting of one 
or more differential amplifier. By properly selecting the external components, it can be 
used to perform a variety of mathematical operations.10. Mention the characteristics of 
an ideal op-amp.
* Open loop voltage gain is infinity.
* Input impedance is infinity.
* Output impedance is zero.
* Bandwidth is infinity.
* Zero offset.
11.  What happens when the common terminal of V+ and V- sources is not 
grounded?
If  the  common point  of the  two supplies  is  not  grounded, twice  the  supply  
voltage  will get applied and it may damage the op-amp.
12. Define input offset voltage.
A small voltage applied to the input terminals to make the output voltage as z ero 
when the two input terminals are grounded is called input offset voltage
13. Define input offset current. State the reasons for the offset currents at the input 
of the op-amp.
The difference between the bias currents at the input terminals of the op-amp is 
called as input offset current. The input terminals conduct a small value of dc current to 
bias the input  transistors  .Since  the  input  transistors  cannot  be  made  identical, there  
exists  a  difference in bias currents.
14. Define CMRR of an op-amp.
The relative sensitivity of an op-amp to a difference signal as compared to a 
common â€" mode signal is called the common â€"mode rejection ratio. It is expressed in 
decibels.
CMRR= Ad/Ac 
15. In practical op- amps, what is the effect of high frequency on its performance?
The  open-loop gain of  op-amp decreases  at  higher  frequencies  due  to the  
presence  of  parasitic  capacitance. The closed-loop gain increases at higher frequencies 
and leads to
Instability 
16. Define slew rate.
The  slew  rate  is  defined  as  the  maximum  rate  of  change  of  output  voltage  
caused by  a step input  voltage. An ideal slew rate is infinite which means that op-amp’s 
output voltage should change instantaneously in response to input step voltage.
17. Mention any two audio frequency oscillators:
• RC phase shift oscillator
• Wein bridge oscillator
18. Mention some of the linear applications of op â€" amps:
Adder, subtra ctor, voltage â€"to- current converter, current â€"to- voltage converters, 
instrumentation amplifier, analog computation, power amplifier, etc are some of the 
linear op-amp circuits.
19. Mention some of the non â€" linear applications of op-amps:-
Rectifier, peak detector, clipper, clamper, sample and hold circuit, log amplifier, 
anti â€"log amplifier, multiplier are some of the non â€" linear op-amp circuits.
20. What are the areas of application of non-linear op- amp circuits?
• .Industrial instrumentation
• Communication
• Signal processing

PART-B

1. Explain the working principle of operational amplifier.
2. Explain the working principle of oscillators
3. Ex plain the types of feedback amplifiers
4. Explain the types of differential amplifiers.

UNIT â€" V - PULSE CIRCUITS
1. What is a multivibrator?
Multivibrators are a group of regenerative circuits that are used extensively in 
timing applications. It is a wave shaping circuit which gives symmetric or asymmetric 
square output. It has two states stable or quasi- stable depending on the type of 
multivibrator.
2. What do you mean by monostable multivibrator?
Monostable multivibrator is one which generates a single pulse of specified 
duration in response to each external trigger signal. It has only one stable state. 
Application of a trigger causes a change to the quasi-stable state. An external trigger 
signal generated du e to charging and discharging of the capacitor produces the transition 
to the original stable state.
3. What is an astable multivibrator?
Astable multivibrator is a free running oscillator having two quasi-stable states. 
Thus, there is an oscillation between these two states and no external signal is required to 
produce the change in state.
4. What is a bistable multivibrator?
Bistable multivibrator is one that maintains a given output voltage level unless an 
external trigger is applied. Application of an external trigger signal causes a change of 
state, and this output level is maintained indefinitely until a second trigger is applied. 
Thus, it requires two external triggers before it returns to its initial state.
5. What are the requirements for producing sustained o scillations in feedback 
Circuits?
For sustained oscillations, the total phase shift around the loop must be zero at the 
desired frequency of oscillation. At desired frequency, the magnitude of the loop gain | A 
b | should be equal to unity
6. Mention any two audio frequency oscillators:
• RC phase shift oscillator
• Wein bridge oscillator
7. What is a filter?
Filter is a frequency selective circuit that passes signal of specified band of 
frequencies and attenuates the signals of frequencies outside the band
8. What are the demerits of passive filters?
Passive filters works well for high frequencies. But at audio frequencies, the 
inductors become problematic, as they become large, heavy and expensive. For low 
fre quency applications, more number of turns of wire must be used which in turn adds to 
the series resistance degrading inductor’s performance ie, low Q, resulting in high power 
dissipation.
9. What are the advantages of active filters?
Active filters used op- amp as the active element and resistors and capacitors as 
passive elements. By enclosing a capacitor in the feed back loop , inductor less active 
filters can be obtained.Op-amp used in non  â€" inverting configuration offers high input 
impedance and low output impedance, thus improving the load drive capacity.
10. Mention some commonly used active filters:
• Low pass filter
• High pass filter
• Band pass filter
• Band reject filter.
11. Mention some applications of 555 ti mer:
• Oscillator
• Pulse generator
• Ramp and square wave generator
• Mono-shot multivibrator
• Burglar alarm
• Traffic light control.
12. List the applications of 555 timers in monostable mode of operation:
• Missing pulse detector
• Linear ramp generator
• Frequency divider
• Pulse width modulation.
13. List the applications of 555 timers in Astable mode of operation:
• FSK generator
• Pulse-position modulator
14. Define combinational logic
When logic gates are connected together to produce a specified output for certain 
specified combinations of input variables, with no storage involved, the resulting circuit 
is called combin ational logic.
15. Explain the design procedure for combinational circuits
• The problem definition
• Determine the number of available input variables & required O/P variables.
• Assigning letter symbols to I/O variables
• Obtain simplified Boolean expression for each O/P.
16. Define half adder and full adder
The logic circuit that performs the addition of two bits is a half adder. The circuit 
that performs the addition of three bits is a full adder.
17. Define Decoder?
A decoder is a multiple - input multiple output logic circuits that converts coded 
inputs into coded outputs where the input and output codes are different.
18. What is binary decoder?
A decoder is a combinational circuit that converts binary information from n i nput 
lines to a maximum of 2n out puts lines.
19. Define Encoder?
An encoder has 2n input lines and n output lines. In encoder the output lines 
generate the binary code corresponding to the input value.
20. What is priority Encoder?
A priority encoder is an encoder circuit that includes the priority function. In 
priority encoder, if 2 or more inputs are equal to 1 at the same time, the input having the 
highest priority will take precedence.

PART-B
1. Explain the RC wave shaping circuits 
2. Explain the Diode clampers 
3. Explain the working of clippers 
4. Explain the types of each Multivibrators 
5. Explain the Schmitt triggers.


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