1017 + Mcqs in Electronic Devices And Circuits Page 5 McqOptions

201.	What is the maximum collector efficiency of a transformer coupled class A power amplifier?
A.	30%
B.	80%
C.	45%
D.	50%
Answer» E.

Discussion

202.	The main feature(s) of a large-signal amplifier is (are) the .
A.	circuit\s power efficiency
B.	maximum amount of power that the circuit is capable of handling
C.	impedance matching to the output
D.	all of the above
Answer» E.

Discussion

203.	For an P-channel enhancement type MOSFET determine the drain current if K = 0.278 x 10-3A/V2, VGS = -4V, VT = -2V, Voltage equivalent at 27°C = 26 mV.
A.	10 mA
B.	1.11 mA
C.	0.751 mA
D.	46.98 mA
Answer» C. 0.751 mA

Discussion

204.	In p type semiconductors the conduction due to holes ( = σp ) is (where e = charge on hole, μp is hole mobility and p is hole concentration)
A.	[A].
B.	[B].
C.	peμp
D.	[D].
Answer» D. [D].

Discussion

205.	The small signal input impedance of a transistor whose output is shorted for the measuring signal is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

206.	Consider the following statements about conditions that make a metal semiconductor contact rectifying N type semiconductor with work function φs more than work function φM of metalN type semiconductor with work function φs less than work function φM of metalP type semiconductor with work function φs more than work function φM of metalP type semiconductor with work function φs less than work function φM of metal. Of these statements
A.	1 and 3 are correct
B.	2 and 3 are correct
C.	1 and 4 are correct
D.	2 and 4 are correct
Answer» B. 2 and 3 are correct

Discussion

207.	In a bipolar junction transistor adc = 0.98, ICO= 2 μA and 1B = 15 μA. The collector current IC is
A.	635 mA
B.	735 mA
C.	835 mA
D.	935 mA
Answer» C. 835 mA

Discussion

208.	For BJT transistor. The maximum power dissipation is specified as 350 mW if ambient temperature is 25°C. If ambient temperature is 60°C the maximum power dissipation should be limited to about
A.	100 mW
B.	250 mW
C.	450 mW
D.	600 mW
Answer» C. 450 mW

Discussion

209.	CE saturation resistance of n-p-n transistor is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

210.	In bipolar transistors dc current gain is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

211.	If aac for transistor is 0.98 then βac is equal to
A.	51
B.	49
C.	47
D.	45
Answer» C. 47

Discussion

212.	For bipolar transistor
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

213.	A diode is operating in forward region and the forward voltage and current are v = 3 + 0.3 sin ωt (volts) and i = 5 + 0.2 sin ωt (mA). The average power dissipated is
A.	15 mW
B.	about 15 mW
C.	1.5 mW
D.	about 1.5 mW
Answer» C. 1.5 mW

Discussion

214.	In the equation i = I0 (eV/ηVT - 1), VT =
A.	[A].
B.	[B].
C.	T x 11600
D.	[D].
Answer» C. T x 11600

Discussion

215.	A voltage of 9 V is applied in forward direction to a semiconductor diode in series with a load resistance of 1000 &ohm;. The voltage across the load resistance is zero. It indicates that
A.	diode is short circuited
B.	diode is open circuited
C.	resistor is open circuited
D.	diode is either o.c or s.c
Answer» C. resistor is open circuited

Discussion

216.	Conductivity σ, mobility μ and Hall coefficient KH are related as
A.	μ = σKH
B.	σ = μKH
C.	KH = μσ
D.	KH =(μσ)1.1
Answer» B. σ = μKH

Discussion

217.	Diffusion constants Dp, Dn mobility μp, μn and absolute temperature T are related as
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

218.	If μn is mobility of free electron and μp is mobility of holes then for silicon at 300 K
A.	μn = μp
B.	μn > μp
C.	μn < μp
D.	μn may be more or less than μp
Answer» C. μn < μp

Discussion

219.	The current density J, free electron mobility μn, hole mobility μp , magnitude of free electron and hole concentration ni electric field E and charge on electron e, in intrinsic semiconductor are related as
A.	J = (μn + μp)eniE
B.	J =
C.	J =
D.	J =
Answer» B. J =

Discussion

220.	The reverse saturation current depends on the reverse bias.
A.	True
B.	False
Answer» C.

Discussion

221.	The mean life time of carrier may range from 10-9 seconds to hundreds of μ-seconds.
A.	True
B.	False
Answer» B. False

Discussion

222.	In a vacuum triode μ = rpgm.
A.	True
B.	False
Answer» B. False

Discussion

223.	Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C. Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not a correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not a correct explanation of A

Discussion

224.	Ripple factor is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» B. [B].

Discussion

225.	All of the following elements have three valence electrons EXCEPT
A.	boron
B.	indium
C.	gallium
D.	arsenic
Answer» E.

Discussion

226.	Which of the following insulating material is restricted to temperatures below 100°C?
A.	Micanite
B.	Asbestos
C.	Teflon
D.	Polythene
Answer» E.

Discussion

227.	Which one of the following material has the highest dielectric strength?
A.	Porcelain
B.	Soft rubber
C.	Glass
D.	polystyrene
Answer» C. Glass

Discussion

228.	An n type semiconductor is illuminated by a steady flux of photons with energy greater than the band gap energy. The change in conductivity Δσ obeys which relation? [ Here, e is the electron charge, μn electron mobility, μp hole mobility, Δn (Δp) is the excess electron (hole) density ].
A.	Δσ = 0
B.	Δσ = e(σn + σp) Δn
C.	Δσ = e(μnΔn - μpΔp)
D.	Δσ = e μnΔn
Answer» C. Δσ = e(μnΔn - μpΔp)

Discussion

229.	The inductance of a single layer solenoid of 10 turns is 5 μH. Which one of the following is the correct value of inductance when the number of turns is 20 and the length is doubled.
A.	10 μH
B.	20 μH
C.	40 μH
D.	5 μH
Answer» B. 20 μH

Discussion

230.	For a UJT ifR1 = Resistor from emitter to the base 1R2 = Resistor from emitter to the base 2 and RBB = R1 + R2, then the intrinsic stand off ratio (η) is
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» E.

Discussion

231.	The residual resistivity of a binary alloy at 0°K is
A.	the sum of the residual resistivities of the component metals
B.	the difference of the residual resistivities of the component metals
C.	the product of the residual resistivities of the component metals
D.	depend on the concentration of the minor component in the alloy
Answer» E.

Discussion

232.	In a P-type semiconductor, the conductivity due to holes (= σP) is equal to e = charge of hole, μP = hole mobility, P = hole concentration,
A.	[A].
B.	[B].
C.	P.e.μP
D.	[D].
Answer» D. [D].

Discussion

233.	The ac resistance of a forward biased p-n junction diode operating at a bias voltage V and carrying current 'I' is
A.	0
B.	constant value independent of V and I
C.	[C].
D.	[D].
Answer» D. [D].

Discussion

234.	If a coil has diameter 'd' number of turns 'N' and form factor F then the inductance of the coil is proportional to
A.	N2dF
B.	Nd2F
C.	[C].
D.	[D].
Answer» E.

Discussion

235.	In a junction transistor biased for operation at emitter current 'IE' and collector current 'IC' the transconductance 'gm' is.
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» C. [C].

Discussion

236.	Calculate the stability factor and change in IC from 25°C to 100°C for, β = 50, RB/ RE = 250, ΔIC0 = 19.9 nA for emitter bias configuration.
A.	42.53, 0.85 μA
B.	40.91, 0.58 μA
C.	40.91, 0.58 μA
D.	41.10, 0.39 μA
Answer» B. 40.91, 0.58 μA

Discussion

237.	The diode and the moving coil milliammeter of figure are assumed to be ideal. The meter reading is
A.	0.1 mA
B.	[B].
C.	[C].
D.	[D].
Answer» E.

Discussion

238.	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.
A.	30 pA
B.	40 pA
C.	50 pA
D.	60 pA
Answer» C. 50 pA

Discussion

239.	Consider the following statement S1 and S2. S1: The β of a bipolar transistor reduces if the base width is increased. S2: the β of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct?
A.	S1 is False, S2 is true
B.	S1 and S2 both are true
C.	S1 and S2 both are false
D.	S1 is true, S2 is false
Answer» E.

Discussion

240.	The impurity commonly used for realizing the base region of a n-p-n transistor is
A.	gallium
B.	indium
C.	boron
D.	phosphorus
Answer» D. phosphorus

Discussion

241.	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 -ve feedback amplifier using the above amplifier with a feedback factor of 0.2 is
A.	1/11 k&ohm;
B.	1/5 k&ohm;
C.	5 kW
D.	11 kW
Answer» B. 1/5 k&ohm;

Discussion

242.	A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. h = 6.6 x 10-34 J sec.
A.	2.26 eV
B.	1.98 eV
C.	1.17 eV
D.	0.74 eV
Answer» B. 1.98 eV

Discussion

243.	An n type silicon bar 0.1 cm long and 100 μm2 in cross-sectional area has a majority carrier concentration of 5 x 1020/m3 and the carrier mobility is 0.13 m0/V-s at 300k. If the charge of an electron is 1.6 x 10-19 coulomb, then the resistance of the bar is
A.	106 ohm
B.	104 ohm
C.	10-1 ohm
D.	10-4 ohm
Answer» D. 10-4 ohm

Discussion

244.	Choose the correct match for input resistance of various amplifier configurations shown below configuration.CB : Common Base LO : LowCC : Common Collector MO : moderateCE : Common EmitterHI: High
A.	CB-LO, CC-MO, CE-HI
B.	CB-LO, CC-HI, CE-MO
C.	CB-MO, CC-HI, CE-LO
D.	CB-HI, CC-LO, CE-MO
Answer» C. CB-MO, CC-HI, CE-LO

Discussion

245.	In given figure a silicon diode is carrying a constant current of 1 mA. When the temperature of the diode is 20°C, VD is found to be 700 mV. If the temperature rises to 40°C, VD becomes approximately equal to
A.	747 mV
B.	660 mV
C.	680 mV
D.	700 mV
Answer» B. 660 mV

Discussion

246.	- ve feedback in an amplifier
A.	reduces gain
B.	increase frequency and phase distortion
C.	reduce bandwidth
D.	increase noise
Answer» B. increase frequency and phase distortion

Discussion

247.	The static characteristic of an adequately forward biased P-n junction is a straight line, if the plot is of __________ Vs → versus
A.	log I Vs log V
B.	log I Vs V
C.	I Vs log V
D.	I Vs V
Answer» C. I Vs log V

Discussion

248.	The fT of a BJT is related to its gm, Cp and Cμ as follows.
A.	[A].
B.	[B].
C.	[C].
D.	[D].
Answer» E.

Discussion

249.	An one sided abrupt junction has 1021/m3 of dopants on the lightly doped side, zero bias voltage and a built-in potential of 0.2 V. The depletion width of abrupt junction.(q = 1.6 x 10-19 C, εr =16, ε0 = 8.87 x 10-12 F/m) is
A.	0.036 nm
B.	0.6 μm
C.	3 mm
D.	1.5 mm
Answer» C. 3 mm

Discussion

250.	Assertion (A): A p-n junction has high resistance in reverse direction.Reason (R): When a reverse bias is applied to p-n junction, the width of depletion layer increases.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not a correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not a correct explanation of A

Discussion

Explore topic-wise MCQs in Electronics & Communication Engineering.

What is the maximum collector efficiency of a transformer coupled class A power amplifier?

The main feature(s) of a large-signal amplifier is (are) the .

For an P-channel enhancement type MOSFET determine the drain current if K = 0.278 x 10-3A/V2, VGS = -4V, VT = -2V, Voltage equivalent at 27°C = 26 mV.

In p type semiconductors the conduction due to holes ( = σp ) is (where e = charge on hole, μp is hole mobility and p is hole concentration)

The small signal input impedance of a transistor whose output is shorted for the measuring signal is

In a bipolar junction transistor adc = 0.98, ICO= 2 μA and 1B = 15 μA. The collector current IC is

For BJT transistor. The maximum power dissipation is specified as 350 mW if ambient temperature is 25°C. If ambient temperature is 60°C the maximum power dissipation should be limited to about

CE saturation resistance of n-p-n transistor is

In bipolar transistors dc current gain is

If aac for transistor is 0.98 then βac is equal to

For bipolar transistor

A diode is operating in forward region and the forward voltage and current are v = 3 + 0.3 sin ωt (volts) and i = 5 + 0.2 sin ωt (mA). The average power dissipated is

In the equation i = I0 (eV/ηVT - 1), VT =

A voltage of 9 V is applied in forward direction to a semiconductor diode in series with a load resistance of 1000 &ohm;. The voltage across the load resistance is zero. It indicates that

Conductivity σ, mobility μ and Hall coefficient KH are related as

Diffusion constants Dp, Dn mobility μp, μn and absolute temperature T are related as

If μn is mobility of free electron and μp is mobility of holes then for silicon at 300 K

The current density J, free electron mobility μn, hole mobility μp , magnitude of free electron and hole concentration ni electric field E and charge on electron e, in intrinsic semiconductor are related as

The reverse saturation current depends on the reverse bias.

The mean life time of carrier may range from 10-9 seconds to hundreds of μ-seconds.

In a vacuum triode μ = rpgm.

Assertion (A): The reverse saturation current in a semiconductor diode is 4nA at 20°C and 32 nA at 50°C. Reason (R): The reverse saturation current in a semiconductor diode doubles for every 10°C rise in temperature.

Ripple factor is

All of the following elements have three valence electrons EXCEPT

Which of the following insulating material is restricted to temperatures below 100°C?

Which one of the following material has the highest dielectric strength?

An n type semiconductor is illuminated by a steady flux of photons with energy greater than the band gap energy. The change in conductivity Δσ obeys which relation? [ Here, e is the electron charge, μn electron mobility, μp hole mobility, Δn (Δp) is the excess electron (hole) density ].

The inductance of a single layer solenoid of 10 turns is 5 μH. Which one of the following is the correct value of inductance when the number of turns is 20 and the length is doubled.

For a UJT ifR1 = Resistor from emitter to the base 1R2 = Resistor from emitter to the base 2 and RBB = R1 + R2, then the intrinsic stand off ratio (η) is

The residual resistivity of a binary alloy at 0°K is

In a P-type semiconductor, the conductivity due to holes (= σP) is equal to e = charge of hole, μP = hole mobility, P = hole concentration,

The ac resistance of a forward biased p-n junction diode operating at a bias voltage V and carrying current 'I' is

If a coil has diameter 'd' number of turns 'N' and form factor F then the inductance of the coil is proportional to

In a junction transistor biased for operation at emitter current 'IE' and collector current 'IC' the transconductance 'gm' is.

Calculate the stability factor and change in IC from 25°C to 100°C for, β = 50, RB/ RE = 250, ΔIC0 = 19.9 nA for emitter bias configuration.

The diode and the moving coil milliammeter of figure are assumed to be ideal. The meter reading is

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.

Consider the following statement S1 and S2. S1: The β of a bipolar transistor reduces if the base width is increased. S2: the β of a bipolar transistor increases if the doping concentration in the base is increased. Which one of the following is correct?

The impurity commonly used for realizing the base region of a n-p-n transistor is

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 -ve feedback amplifier using the above amplifier with a feedback factor of 0.2 is

A particular green LED emits light of wavelength 5490, Å, the energy bandgap of the semiconductor material used there is .. h = 6.6 x 10-34 J sec.

An n type silicon bar 0.1 cm long and 100 μm2 in cross-sectional area has a majority carrier concentration of 5 x 1020/m3 and the carrier mobility is 0.13 m0/V-s at 300k. If the charge of an electron is 1.6 x 10-19 coulomb, then the resistance of the bar is

Choose the correct match for input resistance of various amplifier configurations shown below configuration.CB : Common Base LO : LowCC : Common Collector MO : moderateCE : Common EmitterHI: High

In given figure a silicon diode is carrying a constant current of 1 mA. When the temperature of the diode is 20°C, VD is found to be 700 mV. If the temperature rises to 40°C, VD becomes approximately equal to

- ve feedback in an amplifier

The static characteristic of an adequately forward biased P-n junction is a straight line, if the plot is of __________ Vs → versus

The fT of a BJT is related to its gm, Cp and Cμ as follows.

An one sided abrupt junction has 1021/m3 of dopants on the lightly doped side, zero bias voltage and a built-in potential of 0.2 V. The depletion width of abrupt junction.(q = 1.6 x 10-19 C, εr =16, ε0 = 8.87 x 10-12 F/m) is

Assertion (A): A p-n junction has high resistance in reverse direction.Reason (R): When a reverse bias is applied to p-n junction, the width of depletion layer increases.