GATE ECE topic:electronic-devices PYQs & Answers — Page 2

Questions 11–20 of 20. Imported answers require independent review unless marked reviewed.

For an n-channel silicon MOSFET with 10 nm gate oxide thickness, the substrate sensitivity

is found to be 50 mV/V at a substrate voltage

V, where

is the threshold voltage of the MOSFET. Assume that,

, where

is the separation between the Fermi energy level

and the intrinsic level

in the bulk. Parameters given are

Electron charge

C Vacuum permittivity

F/m Relative permittivity of silicon

Relative permittivity of oxide

The doping concentration of the substrate is

Your answerChoose one option.

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A silicon P-N junction is shown in the figure. The doping in the P region is

and doping in the N region is

. The parameters given are

Built-in voltage (

) = 0.8 V

Electron charge (

) =

Vacuum permittivity (

) =

F/m

Relative permittivity of silicon (

) = 12

The magnitude of reverse bias voltage that would completely deplete one of the two regions (P or N) prior to the other (rounded off to one decimal place) is ________ V.

Diagram for Electronics and Communication Engineering question 42

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For the transistor

in the circuit shown in the figure,

and

, where

is the mobility of electron,

is the oxide capacitance per unit area,

is the width and

is the length. The channel length modulation coefficient is ignored. If the gate-to-source voltage

is 1 V to keep the transistor at the edge of saturation, the threshold voltage of the transistor (rounded off to one decimal place) is ______ V.

Diagram for Electronics and Communication Engineering question 44

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A single crystal intrinsic semiconductor is at a temperature of 300 K with effective density of states for holes twice that of electrons. The thermal voltage is 26 mV.

The intrinsic Fermi level is shifted from mid-band energy level by

Your answerChoose one option.

18.02 meV.

9.01 meV.

13.45 meV.

26.90 meV.

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Consider the recombination process via bulk traps in a forward biased

homojunction diode. The maximum recombination rate is

. If the electron and the hole capture cross-sections are equal, which one of the following is FALSE?

Your answerChoose one option.

With all other parameters unchanged,

decreases if the intrinsic carrier density is reduced.

occurs at the edges of the depletion region in the device.

depends exponentially on the applied bias.

With all other parameters unchanged,

increases if the thermal velocity of the carriers increases.

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A one-sided abrupt

junction diode has a depletion capacitance

of 50 pF at a reverse bias of 0.2 V. The plot of

versus the applied voltage

for this diode is a straight line as shown in the figure below. The slope of the plot is ______

Diagram for Electronics and Communication Engineering question 31

Your answerChoose one option.

−5.7

−3.8

−1.2

−0.4

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The band diagram of a

-type semiconductor with a band-gap of 1 eV is shown. Using this semiconductor, a MOS capacitor having

nF/cm

and a metal work function of 3.87 eV is fabricated. There is no charge in the oxide. If the voltage across the capacitor is

, the magnitude of depletion charge per unit area (in C/cm

) is

Diagram for Electronics and Communication Engineering question 32

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The base of an

BJT T1 has a linear doping profile

as shown below. The base of another

BJT T2 has a uniform doping

. All other parameters are identical for both the devices. Assuming that the hole density profile is the same as that of doping, the common-emitter current gain of T2 is

Diagram for Electronics and Communication Engineering question 33

Your answerChoose one option.

approximately 2.0 times that of T1.

approximately 0.3 times that of T1.

approximately 2.5 times that of T1.

approximately 0.7 times that of T1.

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junction solar cell of area 1.0 cm

, illuminated uniformly with 100 mW cm

, has the following parameters: Efficiency = 15%, open circuit voltage = 0.7 V, fill factor = 0.8, and thickness = 200 μm. The charge of an electron is

C. The average optical generation rate (in cm

) is

Your answerChoose one option.

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An enhancement MOSFET of threshold voltage 3 V is being used in the sample and hold circuit given below. Assume that the substrate of the MOS device is connected to

V. If the input voltage

lies between

V, the minimum and the maximum values of

required for proper sampling and holding respectively, are

Diagram for Electronics and Communication Engineering question 36

Your answerChoose one option.

3 V and

10 V and

13 V and

10 V and

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GATE ECE topic:electronic-devices PYQs

Question 30

Question 42

Question 44

Question 6

Question 7

Question 31

Question 32

Question 33

Question 34

Question 36