Marathon Series EDC for ESE & GATE EC Exams

Question 1

Fermi energy level for p-type semiconductor lies

Question 2

At what condition does the Fermi energy level (E_F) lie exactly between the band gap for intrinsic semiconductor?

Question 3

Considers a silicon semiconductor at T = 300 K in which acceptor concentration N_a = 10¹⁶ cm^–3 and donor concentration N_d = 3 × 10¹⁵ cm^–3. Then the type of the compensated semiconductor and the minority carrier concentration are?

(Assume complete impurity ionization and intrinsic carrier concentration n_i = 1.5 × 10¹⁰ cm^–3)

Question 4

For an npn BJT transistor, how does the common-emitter current gain β depend on the relative dopings of the base region and the emitter region, N_A/N_D and the width of base W?

Question 5

An idea MOS diode is fabricated on a p-type silicon substrate having a doping concentration of N_A = 10¹⁶ cm^-3. What is the work-function ϕ_s (eV) of the silicon substrate at room temperature?

(for silicon, E_g = 1.1eV, ϕ_x = 4.05 eV), n_i = 1.5 × 10¹⁰ cm^-3 at 300 K, V_T = 26 mV)

Question 6

A MOS capacitor has an oxide layer thickness of 300 Å and flat band voltage of –1.3 V, the effective positive charge at the semiconductor oxide layer interface Q_s = 5.5 ×

C/cmThe metal semiconductor work function potential difference Φ_ms is __________ mV. (Assume

and

F/cm.

Question 7

If a material is having a bandgap of 1.73 eV, then the wavelength of photons emitted from it will be ______________ x

cm.

Question 8Multiple Correct Options

A PN junction ‘1’ with

has reverse breakdown voltage

and depletion capacitance

. Another PN junction ‘2’ with

has reverse breakdown voltage

and depletion capacitance

. Which among the following is true?

Question 9

At

reverse saturation current of a germanium diode is

. If it is forward biased by

, then the current in amperes through the diode is____

Question 10Multiple Correct Options

In a tunnel diode, which of the following is/are true.

Question 11

A photo diode has a quantum efficiency of

when photons of energy

are incident upon it. Then the incident optical power in μW required to obtain a photocurrent of

is____

Question 12

What is the ratio of Minimum Conductivity to Intrinsic Conductivity of a material when the Mobility of electron is two times the mobility of hole.

Question 13

An ideal n–channel MOSFET has the following parameters : mobility of electrons

= 500 cm² /V–sec, threshold voltage V_TN = 0.6V and oxide thickness t_ox = 200Å. The MOSFET is biased in the saturation region at V_GS = 5 V to get the saturation drain current (I_{D (sat)}) of 6 mA, the required aspect ratio is _______________.

(Assume that the permittivity of oxide layer is 34.5 × 10^–14 F/ cm)

Question 14

Find the ratio of Transconductance of MOSFET when it is operating in sub threshold region to the Saturation Region

Question 15

Consider a silicon PN junction at T = 300 k with acceptor concentration of N_a = 10¹⁸ cm^–3 and donor concentration of N_d = 10¹⁵ cm^–3. If we change the acceptor doping concentration to N_a = 10¹⁶ cm^–3 by keeping all other parameters constant, then the percentage decrease in built – in potential of the junction will be equal to ________ %.

₍Assume n_i = 1.5 × 10¹⁰ cm^–3, kT = 0.026 eV)

Question 16

An npn BJT having uniform doping of

is operating in inverse active region with

, shown below. The minority carrier concentration at x=

is _______

()

Question 17

For an n–channel E – MOSFET used in the circuit shown below, the threshold voltage, V_T = 1V, the channel length modulation parameter

= 0 and

= 0.3 mA/V². Then the output voltage V_o is

Question 18

A depletion type N-channel MOSFET is biased in linear region for use as a voltage controlled resistor. At V_GS = 4 V, the drain to source resistance (r_ds) found to be 1KΩ, if V_GS is increased to 6 V, then the value of r_ds is _________ KΩ. (Assume, Threshold voltage, V_Th = –1 V, the value of V_DS to be very small )

Question 19

Consider a P- MOS capacitor. Let N_d = 10¹⁵cm^–3,Φ_ms= –0.272 V, t_ox = 500 Å and Q’_ss =10¹⁰cm^–2. What will be the flat-band voltage_________ (in mill volt)?(integer value

Question 20

Consider a MOS structure with P-type silicon. The metal-semiconductor work function difference of ϕ_ms = –0.57V is required. For an aluminum -silicondioxide junction, ϕ′_m = 3.21V and for a silicon-silicon dioxide junction

= 3.20V and E_g = 1 .1 eV if the gate is Aluminum then the acceptor doping concentration to meet the specifications is_________ × 10¹⁰ cm^–3 (upto two decimal places)(kT/q = 26 mV)

Question 21

A silicon abrupt junction in thermal equilibrium at T=300K is doped such that

in n-region and

in the p-region. Consider N_c =

and N_a =

What will be the impurity doping concentrations N_d and N_a in n and p-regions and the built-in potential barrier, V_bi in the p-n junction respectively?

Question 22

Consider a silicon PN junction at T = 300 k with acceptor concentration of N_a = 10¹⁸ cm^–3 and donor concentration of N_d = 10¹⁵ cm^–3. If we change the acceptor doping concentration to N_a = 10¹⁶ cm^–3 by keeping all other parameters constant, then the percentage decrease in built – in potential of the junction will be equal to ________ %.

₍Assume n_i = 1.5 × 10¹⁰ cm^–3, kT = 0.026 eV)

Question 23

A uniformly doped silicon(relative permittivity ε_r=11.7) p-n junction has dopant profile of N_a=N_d=5X10¹⁶ cm^-3. If peak electric field in the junction at breakdown is E = 4X10⁵ V/ cm, then breakdown voltage of this junction is ____V

Question 24Multiple Correct Options

An intrinsic semiconductor is doped with an impurity concentration of

. Assume the intrinsic carrier concentration

and the thermal voltage

. The Fermi level in doped semiconductor

Question 25Multiple Correct Options

A MOSFET carriers a drain current of 2 mA with V_DS = 2V in saturation at λ = 0 what are the possible drain to source resistance when λ = 0.1 V^–1 to λ = 0.3 V^–1