148 + Interview Questions in Electronic Devices and Circuits in Electronics and Communication Engineering Page 3 InterviewSolution

101.	From the given circuit below, we can conclude that.
Answer» According to figure, both the LED is glowing, which indicate that circuit is complete in both the half cycle of a.c. signal. Therefore Emitter and Base junction will act as short circuit in both direction, which indicate transistor is faulty.

Discussion

102.	In a piezoelectric crystal, applications of a mechanical stress would produce
Answer» In piezoelectric materials mechanical stress produces electric polarization.

Discussion

103.	#NAME?
Answer» n type semiconductor is produced when pentavalent impurity is added.

Discussion

104.	In all metals
Answer» In all metals conductivity decreases (and resistance increases) with increase in temperature.

Discussion

105.	The voltage across a zener diode
Answer» Zener diode is always reverse biased.

Discussion

106.	Light dependent resistor is
Answer» Resistance of LDR depends on light.

Discussion

107.	At room temperature the current in an intrinsic semiconductor is due to
Answer» Intrinsic material has equal number of holes and electrons.

Discussion

108.	Work function is the maximum energy required by the fastest electron at 0 K to escape from the metal surface.
Answer» Work function is the minimum energy required by the fastest electron at 0 K to escape from the metal surface.

Discussion

109.	The most commonly used semiconductor material is
Answer» Germanium is rarely used.

Discussion

110.	In which of these is reverse recovery time nearly zero?
Answer» In schottky diode there is no charge storage and hence almost zero reverse recovery time.

Discussion

111.	Calculate the stability factor and change in I from 25°C to 100°C for, β = 50, R/ R = 250, ΔI = 19.9 nA for emitter bias configuration.
Answer» SICO = (1 + β). 51. = 42.53 ΔIC = (SICO).ΔICO = 42.53 x 19.9 nA = 0.85 μA.

Discussion

112.	Work function of oxide coated cathode is much lower than that of tungsten cathode.
Answer» Therefore emission current from oxide coated cathode is more.

Discussion

113.	The word enhancement mode is associated with
Answer» MOSFET may be depletion mode or enhancement mode.

Discussion

114.	In which region of a CE bipolar transistor is collector current almost constant?
Answer» It is used as amplifier when it operates in this region.

Discussion

115.	Secondary emission is always decremental.
Answer» Sometimes it can be useful also.

Discussion

116.	In a degenerate type semiconductor material, the Fermi level,
Answer» This is due to high level of doping.

Discussion

117.	The types of carriers in a semiconductor are
Answer» Holes and electrons.

Discussion

118.	A potential of 7 V is applied to a silicon diode. A resistance of 1 K ohm is also in series with the diode. The current is
Answer»

Discussion

119.	The normal operation of JFET is
Answer» In major portion of drain characteristics ID is constant.

Discussion

120.	The minority carrier life time and diffusion constant in a semiconductor material are respectively 100 microsecond and 100 cm/sec. The diffusion length is
Answer» Diffusion length = .

Discussion

121.	A zener diode is used in
Answer» Zener diode is used only in voltage regulator circuits.

Discussion

122.	A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. = 6.6 x 10 J sec.
Answer» From Plank equation joule to convert it into electron volt it will be divided by 1.6 x 10-19.

Discussion

123.	In a bipolar transistor which current is largest
Answer» Emitter current is larger, collector current is slightly less than emitter current and base current is very small.

Discussion

124.	The - characteristics of a FET is shown in figure. In which region is the device biased for small signal amplification
Answer» Small signal amplifier operation is in constant current region of characteristics.

Discussion

125.	Crossover distortion behaviour is characteristic of
Answer» It is a characteristics of class B output stage as the amplifier is biased in cut-off region. In class B amplifier, two transistor are operated in such a way that one is amplify the half cycle and second is amplify -ve half cycle.

Discussion

126.	If for transistor is 0.98 then β is equal to
Answer» .

Discussion

127.	In an -- transistor biased for operation in forward active region
Answer» In forward active mode emitter base junction is forward biased and base collector junction is reverse biased.

Discussion

128.	An increase in temperature increases the width of depletion layer.
Answer» With increase in temperature width of depletion layer decreases.

Discussion

129.	Recombination produces new electron-hole pairs
Answer» Due to recombination the number of electron-hole pairs is reduced.

Discussion

130.	An amplifier without feedback has a voltage gain of 50, input resistance of 1 k&ohm; and output resistance of 2.5 k&ohm;. The input resistance of the current shunt - feedback amplifier using the above amplifier with a feedback factor of 0.2 is
Answer» Input Resistance with feedback for current shunt, .

Discussion

131.	As compared to an ordinary semiconductor diode, a Schottky diode
Answer» Cut in voltage in Schottky diode is about 0.3 V as compared to 0.7 V in ordinary semiconductor diode.

Discussion

132.	An LED has a rating of 2 V and 10 mA. It is used along with 6V battery. The range of series resistance is
Answer» R = = 400&ohm;. R must be at least 400&ohm; so that current in LED does not exceed 10 mA.

Discussion

133.	The number of doped regions in PIN diode is
Answer» A PIN diode has p and n doped regions separated by intrinsic layer.

Discussion

134.	A transistor has two - junctions. The batteries should be connected such that
Answer» Emitter-base junction is forward biased and base collector junction is reverse biased.

Discussion

135.	A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately.
Answer» By increasing of temperature by 10°C, Io become double so by increasing temperature 20°C, Io become 4 time than initial value... and it is 40 PA.

Discussion

136.	In a bipolar transistor the barrier potential
Answer» Since there are two p-n junctions, there are two depletion layers and 0.7 V across each layer.

Discussion

137.	At very high temperatures the extrinsic semi conductors become intrinsic because
Answer» Covalent bonds are broken.

Discussion

138.	When a voltage is applied to a semiconductor crystal then the free electrons will flow.
Answer» Since electrons are negatively charged they will flow towards positive terminal.

Discussion

139.	Ferrite have
Answer» Ferrite is a low density material of composition with Fe2O3 x O, where x is a bivalent metal, such as Cobart, Ni, Mn. These magnetic materials having very low loss of current and used in high frequency circuit.

Discussion

140.	In a type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be
Answer» Addition of acceptor atom brings Fermi level closer to valence band.

Discussion

141.	In an -- transistor, the majority carriers in the base are
Answer» Emitter is n type and emits electrons which diffuse through the base.

Discussion

142.	In -- transistor the current I has two components viz. I due to injection of holes from -region to -region and I due to injection of electrons from -region to -region. Then
Answer» Emitter is p-type in p-n-p transistor. Therefore holes are majority carriers.

Discussion

143.	In an channel JFET, the gate is
Answer» Since channel is n type gate must be p type.

Discussion

144.	The amount of photoelectric emission current depends on
Answer» Only the intensity of incident radiation governs the amount of photoelectric emission.

Discussion

145.	In the circuit of figure the function of resistor R and diode D are
Answer» Resistance limits current and diode is reverse connected and therefore protects LED against reverse breakdown.

Discussion

146.	A - junction diode has
Answer» A p-n Junction has all these features.

Discussion

147.	The power dissipation in a transistor is the product of
Answer» Maximum power dissipation occurs at collector junction.

Discussion

148.	A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode is
Answer» Current gain = 1 + β = 100.

Discussion

Explore topic-wise InterviewSolutions in .

From the given circuit below, we can conclude that.

In a piezoelectric crystal, applications of a mechanical stress would produce

#NAME?

In all metals

The voltage across a zener diode

Light dependent resistor is

At room temperature the current in an intrinsic semiconductor is due to

Work function is the maximum energy required by the fastest electron at 0 K to escape from the metal surface.

The most commonly used semiconductor material is

In which of these is reverse recovery time nearly zero?

Calculate the stability factor and change in I from 25°C to 100°C for, β = 50, R/ R = 250, ΔI = 19.9 nA for emitter bias configuration.

Work function of oxide coated cathode is much lower than that of tungsten cathode.

The word enhancement mode is associated with

In which region of a CE bipolar transistor is collector current almost constant?

Secondary emission is always decremental.

In a degenerate type semiconductor material, the Fermi level,

The types of carriers in a semiconductor are

A potential of 7 V is applied to a silicon diode. A resistance of 1 K ohm is also in series with the diode. The current is

The normal operation of JFET is

The minority carrier life time and diffusion constant in a semiconductor material are respectively 100 microsecond and 100 cm/sec. The diffusion length is

A zener diode is used in

A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. = 6.6 x 10 J sec.

In a bipolar transistor which current is largest

The - characteristics of a FET is shown in figure. In which region is the device biased for small signal amplification

Crossover distortion behaviour is characteristic of

If for transistor is 0.98 then β is equal to

In an -- transistor biased for operation in forward active region

An increase in temperature increases the width of depletion layer.

Recombination produces new electron-hole pairs

An amplifier without feedback has a voltage gain of 50, input resistance of 1 k&ohm; and output resistance of 2.5 k&ohm;. The input resistance of the current shunt - feedback amplifier using the above amplifier with a feedback factor of 0.2 is

As compared to an ordinary semiconductor diode, a Schottky diode

An LED has a rating of 2 V and 10 mA. It is used along with 6V battery. The range of series resistance is

The number of doped regions in PIN diode is

A transistor has two - junctions. The batteries should be connected such that

A silicon (PN) junction at a temperature of 20°C has a reverse saturation current of 10 pico Ampere. The reverse saturation current at 40°C for the same bias is approximately.

In a bipolar transistor the barrier potential

At very high temperatures the extrinsic semi conductors become intrinsic because

When a voltage is applied to a semiconductor crystal then the free electrons will flow.

Ferrite have

In a type material the Fermi level is 0.3 eV above valence band. The concentration of acceptor atoms is increased. The new position of Fermi level is likely to be

In an -- transistor, the majority carriers in the base are

In -- transistor the current I has two components viz. I due to injection of holes from -region to -region and I due to injection of electrons from -region to -region. Then

In an channel JFET, the gate is

The amount of photoelectric emission current depends on

In the circuit of figure the function of resistor R and diode D are

A - junction diode has

The power dissipation in a transistor is the product of

A transistor has a current gain of 0.99 in the CB mode. Its current gain in the CC mode is