Test 4 - Electronic Devices | Electronics and Communication (ECE)

Question 1 Multiple Choice (Single Answer)

If P is Passivation, Q is n-well implant, R is metallization and S is soruce/drain diffusion, then the order in which they are carried out in a standard n-well CMOS fabrication process, is

P-Q-R-S
Q-S-R-P
R-P-S-Q
S-R-Q-P

Question 2 Multiple Choice (Single Answer)

At 300 K, for a diode current of 1 mA, a certain germanium diode requires a forward bias of 0.1435V, whereas a certain silicon diode requires a forward bias of 0.718 V. Under the conditions stated above, the closest approximation of the ratio of reverse saturation current in germanium diode to that in silicon diode is

1
5
4 $\times$10³
8 $\times$10³

Question 3 Multiple Choice (Single Answer)

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

30 pA
40 pA
50 pA
60 pA

Question 4 Multiple Choice (Single Answer)

n-type silicon is obtained by doping silicon with

germanium
aluminum
boron
phosphorus

Question 5 Multiple Choice (Single Answer)

The drain current of MOSFET in saturation is given by I_D = K (V_GS-V_T) where K is constant.
The magnitude of the transconductance g_m is

$\dfrac{K(V_{GS}- V_T)^2}{V_{DS}}$
2K (V_GS - V_T)
$\dfrac{I_d}{V_{GS} - V_{DS}}$
$\dfrac{K (V_{GS} - V_T)^2 }{V_{GS}}$

Question 6 Multiple Choice (Single Answer)

For an n-channel enhancement type MOSFET, if the source is connected at a higher potential than that of the bulk, (i.e. V_SB > 0) the threshold voltage V_Tof the MOSFET

remains unchanged
decreases
changes polarity
increases

Question 7 Multiple Choice (Single Answer)

The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge=1.6x10^-19C, thermal voltage=26mV and electron mobility = 1350cm²/V-s

The magnitude of the electric field at x = 0.5 $\mu$m is

1kV/cm
5kV/cm
10 kV/cm
26kV/cm

Question 8 Multiple Choice (Single Answer)

The source of a silicon (n_i = 10¹⁰ per cm³) n – channel MOS transistor has an area of 1 sq ^{_{$\mu m$}} and a depth of 1 ^{_{$\mu m$}}. If the dopant density in the source is 10¹⁹/cm³, the number of holes in the source region with the above volume is approximately.

10⁷
100
10
0

Question 9 Multiple Choice (Single Answer)

The measured trans conductance gm of an NMOS transistor operating in the linear region is plotted against the gate voltage VG at a constant drain voltage V_D. Which of the following figures represents the expected dependence of g_m on V_G?

Question 10 Multiple Choice (Single Answer)

The silicon sample with unit cross-sectional area shown below is in thermal equilibrium. The following information is given: T=300K, electronic charge=1.6x10^-19C, thermal voltage=26mV and electron mobility = 1350cm²/V-s

The magnitude of the electron drift current density at x = 0.5 $\mu$m is

2.16$\times$10⁴ A/cm²
1.08$\times$10⁴ A/cm²
4.32$\times$10³ A/cm²
.48$\times$10² A/cm²

Question 11 Multiple Choice (Single Answer)

A p ⁺n junction has a built-in potential of 0.8 V. The depletion layer width at a reverse bias of 1.2V is 2 $\mu$m. For a reverse bias of 7.2 V, the depletion layer width will be

4 $\mu$m
4.9 $\mu$m
8 $\mu$m
12 $\mu$m

Question 12 Multiple Choice (Single Answer)

When the gate-to-source voltage (VGS) of a MOSFET with threshold voltage of 400 mV, working in saturation is 900 mV, the drain current in observed to be 1 mA. Neglecting the channel width modulation effect and assuming that the MOSFET is operating at saturation, the drain current for an applied VGS of 1400 mV is

0.5 mA
2.0 mA
3.5 mA
4.0 mA

Question 13 Multiple Choice (Single Answer)

The action of a JFET in its equivalent circuit can best be represented as a

Current Controlled Current Source
Current Controlled Voltage Source
Voltage Controlled Voltage Source
Voltage Controlled Current Source

Question 14 Multiple Choice (Single Answer)

Find the correct match between Group 1 and Group 2:

Group 1	Group 2
E. Varactor diode	1. Voltage reference
F. Pin diode	2. High frequency switch
G. zener diode	3. Tuned circuits
H. Schottky diode	4. Current controlled attenuator

E - 4, F - 2, G - 1, H - 3
E - 2, F - 4, G - 1, H - 3
E - 3, F - 4, G - 1, H - 2
E - 1, F - 3, G - 2, H – 4

Question 15 Multiple Choice (Single Answer)

The given figure is the voltage transfer characteristic of

an NOMS inverter with enhancement mode transistor as load
an NMOS inverter with depletion mode transistor as load
a CMOS inverter
a BJT inverter

Question 16 Multiple Choice (Single Answer)

Directions: Consider a silicon p - n junction at room temperature having the following parameters:
Doping on the n-side = 1 x 10¹⁷ cm^-3
Depletion width on the n-side = 0.1 $\mu$m

The built-in potential of the junction
Depletion width on the p −side = 1.0 $\mu$m
Intrinsic carrier concentration = 1.4 x 10¹⁰ cm^-3
Thermal voltage = 26 mV
Permittivity of free space = 8.85 x 10^-14 F cm^-1
Dielectric constant of silicon = 12
The built-in potential of the junction

is 0.70 V
is 0.76 V
is 0.82 V
Cannot be estimated from the data given

Question 17 Multiple Choice (Single Answer)

Directions : Consider a silicon p - n junction at room temperature having the following parameters:
Doping on the n-side = 1 x 10¹⁷ cm^-3
Depletion width on the n-side = 0.1 $\mu$m
Depletion width on the p −side = 1.0 $\mu$m
Intrinsic carrier concentration = 1.4 x 10¹⁰ cm^-3
Thermal voltage = 26 mV
Permittivity of free space = 8.85 x 10^-14 F cm^-1
Dielectric constant of silicon = 12

The peak electric field in the device is

0.15 MV. cm^-1, directed from p −region to n −region
0.15 MV. cm^-1, directed from n −region to p −region
1 80 MV. cm^-1, directed from p-region to n −region
1.80 MV. cm^-1, directed from n −region to p −region

Test 4 - Electronic Devices | Electronics and Communication (ECE)

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