GATE ECE year:2017 PYQs & Answers — Page 8

Questions 71–80 of 130. Imported answers require independent review unless marked reviewed.

The dependence of drift velocity of electrons on electric field in a semiconductor is shown below. The semiconductor has a uniform electron concentration of

and electronic charge

. If a bias of 5 V is applied across a 1

m region of this semiconductor, the resulting current density in this region, in kA/cm

, is __________.

Diagram for Electronics and Communication Engineering question 36

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A MOS capacitor is fabricated on

-type Si (Silicon) where the metal work function is 4.1 eV and electron affinity of Si is 4.0 eV.

eV, where

and

are the conduction band minimum and the Fermi energy levels of Si, respectively. Oxide

F/cm, oxide thickness

m and electronic charge

C. If the measured flat band voltage of this capacitor is −1 V, then the magnitude of the fixed charge at the oxide-semiconductor interface, in nC/cm

, is ______.

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As shown, a uniformly doped Silicon (Si) bar of length

with a donor concentration

is illuminated at

such that electron and hole pairs are generated at the rate of

, where

. Hole lifetime is

s, electronic charge

, hole diffusion coefficient

and low level injection condition prevails. Assuming a linearly decaying steady state excess hole concentration that goes to 0 at

, the magnitude of the diffusion current density at

, in A/cm

, is __________.

Diagram for Electronics and Communication Engineering question 37

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For a particular intensity of incident light on a silicon

junction solar cell, the photocurrent density (

) is 2.5 mA/cm

and the open-circuit voltage (

) is 0.451 V. Consider thermal voltage (

) to be 25 mV. If the intensity of the incident light is increased by 20 times, assuming that the temperature remains unchanged,

(in volts) will be ________.

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As shown, two Silicon (Si) abrupt

junction diodes are fabricated with uniform donor doping concentrations of

and

in the

-regions of the diodes, and uniform acceptor doping concentrations of

and

in the

-regions of the diodes, respectively. Assuming that the reverse bias voltage is

built-in potentials of the diodes, the ratio

of their reverse bias capacitances for the same applied reverse bias, is ________.

Diagram for Electronics and Communication Engineering question 38

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Two

-channel MOSFETs, T1 and T2, are identical in all respects except that the width of T2 is double that of T1. Both the transistors are biased in the saturation region of operation, but the gate overdrive voltage (

) of T2 is double that of T1, where

and

are the gate-to-source voltage and threshold voltage of the transistors, respectively. If the drain current and transconductance of T1 are

and

, respectively, the corresponding values of these two parameters for T2 are

Your answerChoose one option.

and

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In the figure shown, the

transistor acts as a switch.

Diagram for Electronics and Communication Engineering question 39

For the input

as shown in the figure, the transistor switches between the cut-off and saturation regions of operation, when T is large. Assume collector-to-emitter voltage at saturation

and base-to-emitter voltage

. The minimum value of the common-base current gain (

) of the transistor for the switching should be ________.

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An abrupt

junction (located at

) is uniformly doped on both

and

sides. The width of the depletion region is

and the electric field variation in the

-direction is

. Which of the following figures represents the electric field profile near the

junction?

Your answerChoose one option.

Diagram for Electronics and Communication Engineering question 39 (figure 2)

Diagram for Electronics and Communication Engineering question 39 (figure 3)

Diagram for Electronics and Communication Engineering question 39 (figure 4)

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For the circuit shown, assume that the NMOS transistor is in saturation. Its threshold voltage

and its transconductance parameter

. Neglect channel length modulation and body bias effects. Under these conditions, the drain current

in mA is ____________.

Diagram for Electronics and Communication Engineering question 40

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Assuming that transistors M1 and M2 are identical and have a threshold voltage of 1 V, the state of transistors M1 and M2 are respectively

Your answerChoose one option.

Saturation, Saturation

Linear, Linear

Linear, Saturation

Saturation, Linear

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GATE ECE year:2017 PYQs

Question 36

Question 36

Question 37

Question 37

Question 38

Question 38

Question 39

Question 39

Question 40

Question 40