Download Semiconductor device - E

NEHRU ARTS AND SCIENCE COLLEGE
ELECTRONICS AND COMMUNICATION SYSTEMS
QUESTION BANK
SEMICONDUCTOR DEVICES
CLASS : I B.Sc ECS
UNIT -1
SEMESTER : II
SECTION - A
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A transistor has ........
(1) one pn junction (2) two pn junctions (3) three pn junctions (4) four pn junctions
2. The number of depletion layers in a transis-tor is ........
(1) 4 (2) 3 (3) 1 (4) 2
The base of a transistor is ....... doped.
(1) heavily (2) moderately (3) lightly (4) none of the above
The element that has the biggest size in a transistor is ........
(1) collector (2) base (3) emitter (4) collector-base junction
In a pnp transistor, the current carriers are ........
(1) acceptor ions (2) donor ions (3) free electrons (4)holes
The collector of a transistor is ........ doped.
(1) heavily (2) moderately (3) lightly (4) none of the above
A transistor is a ......... operated device.
(1) current (2) voltage (3) both voltage and current (4)none of the above
In an npn transistor, ....... are the minority carriers.
(1) free electrons (2) holes (3) donor ions (4) acceptor ions
The emitter of a transistor is ........ doped.
(1) lightly (2) heavily (3) moderately (4) none of the above
In a transistor, the base current is about ........ of emitter current.
(1) 25% (2) 20% (3) 35% (4) 5%
At the base-emitter junction of a transistor, one finds ........
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(1) i) reverse bias (2) (ii) a wide depletion layer (3) (iii) low resistance (4) (iv) none of the
above
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. The input impedance of a transistor is ......
(1) high (2) low (3) very high (4) almost zero
Most of the majority carriers from the emit-ter .........
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(1) recombine in the base (2) recombine in the emitter (3)pass through the base region to
the col-lector (4)none of the above
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The current IB is ........
(1) electron current . (2) hole current (3) donor ion current (4) acceptor ion current
In a transistor, ........
(1) IC = IE + IB (2) IB = IC + IE (3) IE = IC ? IB (4) IE = IC + IB
The value of ? of a transistor is ........
(1) more than 1 (2) less than 1 (3) 1 (4) none of the above
IC = ? IE + .........
(1) IB (2) ICEO (3) ICBO (4) ? IB
The output impedance of a transistor is ........
(1) high (2) zero (3) low (4) very low
In a transistor, IC = 100 mA and IE = 100.5 mA. The value of ? is ........
(1) 100 (2) 50 (3) about 1 (4) 200
In a transistor if ? = 100 and collector cur-rent is 10 mA, then IE is ........
(1) 100 mA (2) 100.1 mA (3) 110 mA (4) none of the above
The relation between ? and ? is ......
(1) ? = 1/ 1 ? ? (2) ? =1 ? ? /? (3) ? = ? /1 ? ? (4) none of the above
The value of ? for a transistor is generally ........
(1) 1 (2) less than 1 (3) between 20 and 500 (4) above 500
The most commonly used transistor arrange-ment is ........ arrangement.
(1) common emitter (2) common base (3) common collector (4) none of the above
The input impedance of a transistor con-nected in .......... arrangement is the highest.
(1) common emitter (2) common collector (3) common base (4) none of the above
The output impedance of a transistor con-nected in ......... arrangement is the highest.
(1) common emitter (2) common collector (3) common base (4) none of the above
SECTION – B
1. Discuss about Energy band structure.
2. Describe briefly Semiconductor
3. Explain about Insulator
4. Discuss about Conductor
5. Discuss briefly about Doping process
SECTION – C
1. Explain about Intrinsic Semiconductor.
2. Explain about Extrinsic Semiconductor
3. Explain VI Characteristics of PN junction diode.
UNIT - 3
SECTION - A
A JFET has three terminals, namely......
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(1) cathode, anode, grid (2) emitter, base, collector (3)source, gate, drain (4) none of the
above
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A JFET is also called....... transistor
(1) uni polar (2) bipolar (3) uni junction (4) none of the above
The gate of a JFET is ....... biased.
(1) reverse (2) forward (3) reverse as well as forward(4) none of the above
In a p-channel JFET, the charge carriers are.......
(1) electrons (2) holes (3) both electrons and holes (4)none of the above
A MOSFET can be operated with .........
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(1) negative gate voltage only (2) positive gate voltage only (3) positive as well as
negative gate voltage (4)none of the above
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A MOSFET has ......... terminals
(1) two (2) five (3) four (4) three
A JFET has ...... power gain.
(1) small (2) very high (3) very small (4) none of the above
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The input control parameters of a JFET is..........
(1) gate voltage (2) source voltage (3) drain voltage (4)gate current
In a JFET, when drain voltage is equal to pinch-off voltage, the depletion layer......
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(1) almost touch each other (2) have large gap (3)have moderate gap (4) none of the
above
A JFET has high input impedence because.......
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(1) it is made of semiconductor material (2) input is reverse bias (3) of impurity
atoms (4) none of the above
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........ has the lowest noise- level
(1) trode (2) ordinary transistor (3) tetrode (4) JFET
A MOSFET is sometimes called ....... JFET
(1) many gate (2) open gate (3) insulated gate (4)shorted gate
Which of the following devices has the highest input impedance?
(1) JFET (2) MOSFET (3) crystal diode (4) ordinary transistor
A MOSFET uses the electric field of a ..... to control the channel current
(1) capacitor (2) battery (3) generator (4) none of the above
A JFET is similar in operation to ....... value
(1) diode (2) pentode (3) tetrode (4) triode
A JFET is a ....... driven devices
(1) current (2) voltage (3) both current and voltage (4)none of hte above
The input impedance of a JFET is ..... that of an ordinary transistor
(1) equal to (2) less than (3) more than (4) none of the above
The channel of a JFET is between the......
(1) gate and drain (2) drain and sowrce (3) gate and source (4) input and output
The pinch-off voltage of a JFET is about.....
(1) 5V (2) 0.6V (3) 15V (4) 25V
The gate voltage in a JFET at which drain current becomes zero is called ...... voltage
(1) saturation (2) pinch-off (3) active (4) cut-off
In class A operation, the input circuit of a JFET is....... biased
(1) forward (2) reverse (3) not (4) none of the above
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The pinch-off voltage in a JFET is analogous to ....... voltage in a vaccum tube
(1) anode (2) cathode (3) grid cut-off (4) none of the above
The source terminal of a JFET corresponds to........ of a vaccum tube.
(1) plate (2) cathode (3) grid (4) none of the above
For VGS =0V, the drain current becomes constant when VDS exceeds
(1) cut off (2) VDD (3) VP (4) 0V
A common base configuration of a pnp transistor is analogous to......of a JFET
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(1) common source configuration (2) common drain configuration (3) common gate
configuration (4) none of the above
SECTION – B
1.
2.
3.
4.
5.
Compare CB,CE,CC.
Explain the operation and Working of PNP transistor.
Explain the operation and Working of NPN transistor.
Give the Short notes on thermal run away.
Give the Shprt notes on Heat sink
SECTION – C
1. Explain briefly CE configuration.
2. Explain the CB configuration
3. Explain the CC configuration
UNIT - 2
SECTION - A
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A crystal diode has .......
(1) one pn junction (2) two pn junction (3) three pn junction
a crystal diode has forward resistance of the order of.......
(1) k? (2) ? (3) M?
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If the arrow of crystal diode symbolis positive w.r.t. bar,then diode is ........biased
(1) forwar (2) reverse (3) none of the above
The reverse current in a diode is of the order of.......
(1) kA (2) mA (3) ?A
The forward voltage drop across a silicon diode is about.......
(1) 2.5V (2) 0.7V (3) 10V
A crystal diode is used as.......
(1) an amplifier (2) a rectifier (3) an oscilator
The dc resistance of a crystal diode is....... its ac resistance
(1) less than (2) the same as (3) more than
An ideal crystal diode is one which behaves as a perfect ....... when forward biased.
(1) insulator (2) resistance (3) conductor
the ratio of reverse resistance and forward resistance of a germanium crystal diode is about......
(1) 1:1 (2) 40000:1 (3) 100:1
The leak current in a crystal diode is due to........
(1) minority carriers (2) majority carriers (3) junction
If the temperature of a crystal diode increases, then leakage current........
(1) remains same (2) decreases (3) increases
The PIV reting of a crystal diode is...... that of equivalent vaccum diode.
(1) the same as (2) lower than (3) more than
If the doping level of a crystal diode is increased, the breakdown voltage .........
(1) is decreased (2) remains same (3) is increased
The knee voltage of crystal diode is d voltageapproximately equal to......
(1) barrier potential (2) forward voltage (3) applied voltage
when the crystal diode current is large, the bias is......
(1) inverse (2) poor (3) forward
A crystal diode is a ........ device
(1) non-linear (2) linear (3) bilateral
a crystal diode utilities......... characteristics for rectification
(1) reverse (2) forward (3) forward or reverse
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A zener diode has......
(1) 1 pn junction (2) 2 pn junction (3) 4 pn junction
a zener diode is used as ......
(1) an \amplifier (2) a rectifier (3) a voltage regulator
If the doping level in a crystal diode is increased, the width of the depletion layer ........
(1) is increased (2) is same (3) is decreased
The doping level in a zener diode is........that of a crystal diode.
(1) lessthan (2) more than (3) same as
a zener diode is always .....connected
(1) reverse (2) forward (3) either forward or reverse
When the graph between current through and voltage across a device is a straight line, the
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device is referred to as.......
(1) active (2) passive (3) linear
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A zener diode utilises .......... characteristics for its operation
(1) forward (2) reverse (3) none of the above
The ripple factor of a half-wave rectifier is.......
(1) 0.48 (2) 2 (3) 2.5
SECTION - B
1. What is a tunnel diode?
2. Explain the characteristics of tunnel diode
3. Explain the working of varactor diode.
4. Give the Shortnotes on PIN diode.
5. Discuss the Application of PIN diode
SECTION – C
1. Explain the V-I Characteristics of Zener Diode
2.Explain the working Principle of schockley diode
3.Explain the working Principle of Gunn diode.
UNIT - 4
SECTION – A
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When a crystal diode is used as rectifier, the most important consideration is.........
(1) doping (2) reverse (3) forward (4) PIV rating
In the breakdown region, zener diode behaves like a...... source
(1) constant voltage (2) constant current (3) constant resistance (4) none of the above
there is a need of transformer for........
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(1) half wave rectifier (2) centre- tap full-wavw rectifier (3) bride rectifier (4) none of the
above
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a zener diode is ..... device
(1) non-linear (2) a linear (3) an amplifying (4) none of the above
a zener diode is destroyed if it.....
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(1) is forward biased (2) is reverse biased (3) more than rated currebt (4) none of the
aboive
A series resistance is connected in the zener circuit to........
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(1) reverse bias the zener (2) protect the zener (3)forward bias the zener (4) none of the
above
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A zener diode has ...... breakdown voltage
(1) zero (2) undefined (3) sharp (4) none of the above
FET as______ control device
(1) resistance (2) temp (3) current(4) voltage control
Transistor is........ control device
(1) current (2) resistance (3) voltage (4) temp
SCR is silicon control.......
(1) half- rectifier (2) centre-tap full-wave rectifier (3) rectifier (4) none of the above
A 10v power supply would use....... as filter capacitor
(1) paper capacitor (2) mica capacitor (3) electrolytic capacitor (4) none of the above
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....... rectifier has the lowest forward resistance.
(1) solid state (2) gas tube (3) vaccum tube (4) none of the above
Main ac power is converted into dc power for........
(1) lighting purposes (2) using in electronic equipment(3) heaters (4) none of the above
The disadvantage of a half wave rectifier is that the.......
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(1) components are expensive (2) diodes must have a higher power rating (3) output is
difficult to filter (4)none of the above
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The PIV rating of each diode in a bridge rectifier is....... that of the equivalent centre tap rectifier
(1) one-half (2) the same as (3) twice (4) four times
For the same secondary voltage, the output voltage from a centre -tap rectifier is......than that
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of bridge rectifier
(1) twice (2) thrice (3) 4 times (4) one-half
If the PIV rating of a diode is exceeded,......
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(1) the diode conducts poorly (2) the diode is destroyed(3) the diode behaves as zener
dioide (4) none of the above
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A 10V power supply would use......... asa filter capacitor
(1) paper capacitor (2) air capacitor (3) mica capacitor(4) none of the above
The ......... filter circuits result in the best voltage regulation
(1) capacitor input (2) choke input (3) resistance input(4) none of the above
Zener diodes are used primarily as
(1) amplifier (2) rectifier (3) voltage regulator (4)oscillator
A pn junction that radiates energy as light instead of heat is called a
(1) LED (2) photo diode (3) zener diode (4) photocell
To display the digit 8 in a seven segment indicator
(1) C must be lighted (2) G must be off (3) F must be on(4) all segments must be lighted
A photo diode is normally
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(1) forward biased (2) reverse biased (3) neither forward nor reverse biased (4) emitting
light
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A varactor is usually
(1) forward biased (2) reverse biased (3) unbiased (4)none of the above
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The device associated with voltage controlled capacitance is a
(1) LED (2) photo diode (3) zener diode (4) varactor diode
SECTION – B
1. Discus briefly UJT as relaxation oscillator
2. Describe briefly about the JFET.
3. Compare BJT and UJT
4. Compare JFET and MOSFET
5. Give the Short notes on PUT and DIAC
SECTION – C
1. Explain the working principle of MOSFET.
2. Explain the working principle of UJT
3. Explain the V-I Characteristics of SCR.
UNIT - 5
SECTION – A
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2
The phase difference between the input and output voltages in a common base arrange-ment is
(1) 180 degree (2) 90 degree (3) 0 degree (4) none
The power gain of a transistor connected in ........ arrangement is the highest.
(1) common emitter (2) common base (3) common collector (4) none of the above
The phase difference between the input and output voltages of a transistor connected in
3
common emitter arrangement is ........
(1) 0º (2) 180º (3) 90º (4) 270º
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The voltage gain of a transistor connected in ........ arrangement is the highest.
(1) common base (2) common collector (3) common emitter (4) none of the above
As the temperature of a transistor goes up, the base-emitter resistance ........
(1) decreases (2) increases (3) remains the same (4)none of the above
The voltage gain of a transistor connected in common collector arrangement is .......
(1) equal to 1 (2) more than 10 (3) more than 100 (4)less than 1
The phase difference between the input and output voltages of a transistor connected in
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common collector arrangement is ........
(1) 180º (2) 0º (3) 90º (4) 270º
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IC = ? IB + ........
(1) ICBO (2) ? IE (3) iii) ICEO (4) none of the above
IC = ?/1 ? ? IB + ........
(1) ICEO (2) ICBO (3) IC (4) (1 ? ?) IB
IC?/1 ? ?+IB ....... 1 ? ?
(1) ICBO (2) ICEO (3) IC (4) IE
BC 147 transistor indicates that it is made of ........
(1) germanium (2) silicon (3) carbon (4) none of the above
The collector-base junction in a transistor has ........
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(1) forward bias at all times (2) reverse bias at all time(3) low resistance (4) none of the
above
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The most commonly used semiconductor in the manufacture of a transistor is ........
(1) germanium (2) silicon (3) carbon (4) none of the above
A heat sink is generally used with a transis-tor to ........
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(1) increase the forward current (i (2) decrease the forward current (3) compensate for
excessive doping (4) prevent excessive temperature rise
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The leakage current in CE arrangement is....... that in CB arrangement.
(1) more than (2) l ess than (3) the same as (4) none of the above
The arrow in the symbol of a transistor indi-cates the direction of .........
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(1) electron current in the emitter (2) electron current in the collector (3) hole current in the
emitter (4) donor ion current
In a transistor, signal is transferred from a ........ circuit.
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(1) high resistance to low resistance (2) low resistance to high resistance (3) high
resistance to high resistance (4)low resistance to low resistance
. A transistor is connected in CB mode. If it is now connected in CE mode with same bias
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voltages, the values of IE, IB and IC will ....
(1) remain the same (2) i ncrease (3) decrease (4) none of the above
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An ideal source consists of 5 V in series with 10 k ? resistance. The current magnitude of
equivalent current source is ..............
(1) 2 mA (2) 3.5 mA (3) 0.5 mA (4) none of the above
When the outermost orbit of an atom has more than 4 electrons, the material is gen- erally a
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..............
(1) metal (2) non-metal (3) semiconductor (4) none of the above
When the outermost orbit of an atom has exactly 4 valence electrons, the material is generally
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..............
(1) a metal (2) a non-metal (3) a semiconductor (4) an insulator
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The current output of an ideal current source is ..............
(1) zero (2) constant (3) dependent on load resistance(4) dependent on internal resistance
The output voltage of an ideal voltage source is ..............
(1) zero (2) constant (3) dependent on load resistance(4) dependent on internal resistance
Maximum power is transferred if load resistance is equal to .......... of the source.
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(1) half the internal resistance (2) internal resistance(3) twice the internal
resistance (4) none of the above
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An ideal current source has .............. inter- nal resistance.
(1) infinite (2) zero (3) small (4) none of the above
SECTION - B
1. Discuss about How does photo-diode work ?
2. Give the applications of photo-diodes.
3. Explain the working of a LED.
4. Give the Application of LED
5. Discuss briefly about Photo emissive sensor
SECTION – C
1. Explain about Photo Transistor and Photo Voltaic cell
2. Explain with neat sketch LCD.
3. Explain Briefly about the Opto coupler.
ALL THE BEST