Saturday, May 28, 2011

Basic Electronics Questions for Interview Preparation

1.      How to get high resolution digital output from a normal aDC?
2.      How to radiate an output of a circuit through an antenna wireless (device used)?
3.      Is there any lower limitation of current for a given transistor?
4.      Is there any limitation to the max voltage that can be stepped up by a step up transformer?
5.      Explain 3 dB cutoff frequency? Why is it 3 dB, not 1 dB?
6.      Which semiconductor device is used as a voltage regulator?
7.      What’s the difference between capacitors having polarity leads and the ones which don’t have?
8.      What is meant by pre-emphasis and de-emphasis?
9.      For as asynchronous transmission, is it necessary to supply some synchronizing pulses
Additionally or to supply or to supply start and stop bit?
10.  BPFSK is more efficient than BFSK in presence of noise. Why?
11.   What is a multiplexer?
12.   How can you convert an SR Flip-flop to a JK Flip-flop?
13.   How can you convert a JK Flip-flop to a D Flip-flop?
14.   What is Race-around problem? How can you rectify it?
15.   Which semiconductor device is used as a voltage regulator and why?
16.   Explain an ideal voltage source?
17.   Explain zener breakdown and avalanche breakdown?
18.   What are the different types of filters?
19.   When measuring DC voltage across a device with a multimeter, the meter indicates 0 volts. What is one possible explanation for this reading?
20.   The amount of useful output power provided by a device is 1.5 W. It is powered by a 48V supply with 100 mA of current. How much power is wasted in heat?
21.  As the efficiency of a device DECREASES, which of the following will INCREASE?
 a) Power output b) amplifier gain c) heat output d) output impedance
22.  What is the peak voltage of a sine wave that measures 220 VAC rms?
23.  What is the relationship between current (I) and voltage (E) in a circuit consisting of a capacitor in series with a resistor?
24.  The leads of a multimeter are across a diode in the following manner:

25.  Red lead connects to the end of diode with marking band, and the black lead connects on other end. What does a reading of –0.6 volts indicate?
 a) Forward bias, leads connected with proper polarity
 b) Reverse bias, leads connected with proper polarity
 c) Forward bias, leads connected with reverse polarity
 d) Reverse bias, leads connected with reverse polarity

26.  What does LED stand for?
27.  Name 3 leads of common transistor?
28.  If 2 resistors are connected in parallel then what is the final resistance?
29.  What is the difference between latches and flip flops?
30.  Which type of modulation is used in TV transmission?
31.  Zener diodes are most commonly used in which circuits?
32.  .A path between two or more points along which an electrical current can be carried is called as ________
33.  The frequency of the second harmonic of 60Hz is________
  1. 1 coulomb per second is equal to ________
  2. What is an ideal voltage source?
  3. Why is impedance matching important?
  4. Which device is used to convert direct current to alternating current?
  5. Which breakdown mechanism occurs in lightly doped p-n junction under reverse biased condition?
  6. What is the important characteristic of emitter follower?
  7. The common collector amplifier is known as________
41.  What is band width of AM wave?
42.  What is the DC and RMS voltage value of sine wave?
43.  What is the frequency of operation in Wein Bridge oscillator?
44.  State Barkhausen’s criterion for sustained oscillations?
45.  (1010111)2 = (?)8
46.  As the input voltage increases, drop across the diode__________.
a)      Increases               b) decreases                 c)constant                    d) none of these





47.  The figure below is characteristics graph of ____________.


  1. What is Icbo?
  2. What is alpha cut of frequency?
  3. What is the typical value of a resistivity of conductor?
  4. Base current in pnp transistor is ………..compared to Ie.
  5. What is the relation between alpha and Beta?
  6. What is Zener breakdown?
  7. What is avalanche breakdown?
  8. IC 550 is ………
  9. FET is a …….device.
  10. Movement of charge carriers by an applied voltage is called ………….
  11. Movement of charge carriers from area of higher carrier concentration  to  lower carrier concentration is called …………
  12. In a pn diode with increase in reverse bias ,reverse current ………..
60.  Why is silicon diode preferred when knee voltage of germanium diode is less?
61.  Why Zener diodes are used in voltage regulator?
62.  Why is npn transistor used more compared to pnp?
63.  Why germanium controlled rectifier can’t be used?
64.  What is the use of gate terminal in SCR, when SCR can be triggered without a gate pulse?
65.  Construction of AND gate using diode, require two diodes to be in ______ (series/ parallel).
66.   How is NOR gate used as an inverter?
67.  Criterion to be satisfied for sustained oscillation is_______
68.  What is the output of an integrator, if the input is a square wave?
69.  What is the significance of Q-point in a diode?
70.  What do you mean by punch through effect in transistor?
71.  How will you turn off an SCR?
72.  What are the advantages of negative feedback in an amplifier?
73.  What is the value of slew rate for an ideal opamp?
74.  What will happen if we increase/ decrease the values of R/C in opamp integrator?
75.  How will you turn on SCR other than gate triggering?
76.  What is Peak inverse rating of a diode?
77.  What is ripple factor?
78.  What is transistor biasing?
79.  Name diff. biasing circuits.
80.  What is voltage multiplier?
81.  What is filter? Why is it required?
82.  What are the capacitive effects in a p-n junction?
83.  What do you mean by current gain characteristics of CB configuration for transistor?
84.  Why junction transistors are called bipolar devices?
85.  How is FET diff. from BJT?
86.  What is SCR? Why is it so called?
87.  How do you select a SCR for a given application?
88.  What is snubber circuit? Why is it required?
89.  What is holding current? How is it dependent on the gate-current for SCR?
90.  What is the basic difference between Latches and Flip flops?
91.  What is CMRR? Explain briefly.
92.  What is impulse response?
93.  What is Race-around problem? How can you rectify it?
94.  Which semiconductor device is used as a voltage regulator and why?
95.  What do you mean by an ideal voltage source?
96.  What is a SCR? How is it useful?
97.  Which are the different types of basic oscillator circuits?
  1. Why should core saturation of a conventional impedance matching transformer be avoided?
A. Harmonics and distortion could result
B. Magnetic flux would increase with frequency
C. RF susceptance would increase
D. Temporary changes of the core permeability could result
  1.  What is one reason to use an impedance matching transformer?
A. To reduce power dissipation in the transmitter
B. To maximize the transfer of power
C. To minimize SWR at the antenna
D. To minimize SWR in the transmission line
  1.  Which of the following devices can be used for impedance matching at radio frequencies?
A. A transformer
B. A Pi-network
C. A length of transmission line
D. All of these choices are correct
  1.  Which of the following describes one method of impedance matching between two AC circuits?
A. Insert an LC network between the two circuits
B. Reduce the power output of the first circuit
C. Increase the power output of the first circuit
D. Insert a circulator between the two circuits
  1.  A two-times increase or decrease in power results in a change of how many dB?
A. 2 dB             B. 3 dB             C. 6 dB             D. 12 dB
  1.  What type of capacitor is often used in power-supply circuits to filter the rectified AC?
A.   Disc ceramic         B. Vacuum variable    C. Mica                        D.  Electrolytic
  1.  Which of the following is the primary advantage of ceramic capacitors?
A.            Tight tolerance                    B.             High stability                                  
C.             High capacitance for given volume                       D.            Comparatively low cost
  1.  Which of the following is an advantage of an electrolytic capacitor?
A.            Tight tolerance        B.             Non-polarized
C.             High capacitance for given volume                       D.            Inexpensive RF capacitor
  1. Which of the following is one effect of lead inductance in a capacitor used at VHF and above?
A.             Effective capacitance may be reduced
B.             Voltage rating may be reduced
C.             ESR may be reduced
D.            The polarity of the capacitor might become reversed
  1. What is the main disadvantage of using a conventional wire-wound resistor in a resonant circuit?
A.            The resistor's tolerance value would not be adequate for such a circuit
B.             The resistor's inductance could detune the circuit
C.             The resistor could overheat
D.            The resistor's internal capacitance would detune the circuit
  1. What is the peak-inverse-voltage rating of a rectifier?
A.            The maximum voltage the rectifier will handle in the conducting direction
B.             1.4 times the AC frequency
C.             The maximum voltage the rectifier will handle in the non-conducting direction
D.            2.8 times the AC frequency
  1.  What are the two major ratings that must not be exceeded for silicon-diode rectifiers?
A.             Peak inverse voltage; average forward current
B.             Average power; average voltage
C.             Capacitive reactance; avalanche voltage
D.            Peak load impedance; peak voltage
  1. When two or more diodes are connected in parallel to increase current handling capacity, what is the purpose of the resistor connected in series with each diode?
A.            The resistors ensure the thermal stability of the power supply
B.             The resistors regulate the power supply output voltage
C.             The resistors ensure that one diode doesn't carry most of the current
D.            The resistors act as swamping resistors in the circuit
  1.  Which of the following is an advantage of using a Schottky diode in an RF switching circuit as compared to a standard silicon diode?
A.             Lower capacitance
B.             Lower inductance
C.             Longer switching times
D.            Higher breakdown voltage
  1.  What are the stable operating points for a bipolar transistor that is used as a switch in a logic circuit?
A.             Its saturation and cut-off regions
B.             Its active region (between the cut-off and saturation regions)
C.             Between its peak and valley current points
D.            Between its enhancement and deletion modes
  1.  What is an advantage of the low internal resistance of Nickel Cadmium batteries?
A.            Long life
B.             High discharge current
C.             High voltage
D.            Rapid recharge
  1.  What is the minimum allowable discharge voltage for maximum life of a standard 12 volt lead acid battery?
A.            6 volts          B.             8.5 volts
C.             10.5 volts    D.            12 volts

By Munisah

  1.  What will be the maximum voltage across capacitor?
(a)   0 V                   (b) V                (c) 0 .693 V                  (d) 0.707 V

116.                       
Current flowing through the branches AC, ABC and ADC will be
(a)Equal                 (b) zero            (c) Different           (d) AC > ABC and ABC = ADC
117. Application of starter in tube light
118. The basic circuit used to convert sine wave into a square wave?
119. Which material is basically used for soldering?
120. What is the function of Buffer circuit?
121. Difference between n-type and p-type semi- conductors?
122. Why mainly silicon and germanium  is preferred for making semi conductor devices not others?
123. BJT’s are _____________ controlled device.
124. What is the need of Fourier Transform?
125. What is isolated ground and what is the need for the same?
126. Can we generate any non-periodic wave using electronic circuit?
127.                      Drift current in p-n junction is influenced by what?
128.                      Order of electrical conductivity of pure Si, GaAs, Cu, Nacl at room temperature is___________
129.                      With increasing temperature , the electrical conductivity of the metal___________
130.                      An electric field of 10V/cm applied across a crystal causes the minority carriers to move a distance of 1cm in 20 micro sec.  The mobility (cm2/V-sec) is?
131.                      Hall coefficients are used for what?
132.                      Diffusion constant for free electrons in silicon expressed In cm^2/s is?
133.                      What are injected minority carriers?
134.                      Temperature coefficient of resistivity in an intrinsic semiconductor is positive or negative?
135.                      What is mobility of an electron in a metal?
136.                      How the dynamic resistance of a diode varies with current?
137.                      Built in potential in a P-N junction increases with
             A. Temperature
             B. Doping Level
             C. Equal to difference b/w the Fermi levels of two sides.
             D..Equal to average of Fermi levels of two sides.
138.                      Draw the waveform output waveform for a full wave bridge rectifier with Si diodes for a 1 V p-p input.
139.                      When a diode is forward biased the recombination of free electrons and holes may produce
             A.Heat
             B.Light
             C.Radiation.
              D.All of these.
140.                      FET has an offset voltage of about of
   A. 0.2           B.0.6               C2.2                D.0
141.                      An avalanche photo diode works on
             A.High forward bias
             B. High forward bias and impact ionization
              C.High reverse bias
             D.All of these
142.                      Clamping circuit depends mostly on
              A.Capacitance           B.Time constant
             C.Resistance
           
143.                      Biasing is done to_______________________
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