# An intrinsic semiconductor is doped lightly with p-type impurity. It is found that the conductivity actually decreases till a certain doping level is reached. Why does this occur

1.  The mobility of holes decreases

2.  the mobility of both electrons and holes decreases

3.  the hole density actually reduces

4.  Effect of reduction in electrons due to increase in holes compensate more than the effect of increase in holes on conductivity

4

the mobility of both electrons and holes decreases

Explanation :
No Explanation available for this question

# Assuming that the electron mobility in intrinsic silicon is 1500 cm2/Vs at room temperature (T=300K) and the corresponding volt equivalent of temperature VT=25.9mV,what is the approximate value of the election diffusion constant

1.  40cm2/s

2.  4cm2/s

3.  400cm2/s

4.  4000cm2/s

4

4000cm2/s

Explanation :
No Explanation available for this question

# In a MOSFET, the transfer characteristics can be used to determine which of the following device parameters

1.  Threshold voltage and output resistance

2.  trans conductance and output resistance

3.  Threshold voltage and trans conductance

4.  trans conductance and channel length modulation parameter

4

Threshold voltage and trans conductance

Explanation :
No Explanation available for this question

# Assuming an operating temperature T=300K and corresponding  VT=26mV, what is the change in semiconductor silicon diodes forward voltage VD to produce a 10:1 change in diode forward voltage VD to produce a 10:1 change in diode current ID, while operating in the forward bias region (

1.  60mV

2.  120mV

3.  180mV

4.  240mV

4

120mV

Explanation :
No Explanation available for this question

# The doping concentration on the n-side of a p-n junction diode is enhanced. Which one of the following will get affected

1.  width of the depletion region on n-side

2.  width of the depletion region on p-side

3.  width of the depletion region on both sides

4.  no change in width of depletion regions

4

width of the depletion region on n-side

Explanation :
No Explanation available for this question

# If fc=25MHz, fm=400Hz, Ec=4V, Δf=10kHz then equation of FM wave will be

1.  4sin(1.57x108t+25 sin 2513t)

2.  10sin(1.57x108t+25 sin 2513t)

3.  15sin(1.57x108t+25 sin 2513t)

4.  20sin(1.57x108t+25 sin 2513t)

4

4sin(1.57x108t+25 sin 2513t)

Explanation :
No Explanation available for this question

# When a junction diode is used as a half wave rectifier with purely resistive load and sinusoidal input voltage, what is the value of diode conduction angle(when Φ1 is the ignition angle corresponding to the cut-in voltage )

1.  π

2.  π-Φ1

3.  π- 2Φ1

4.  slightly greater than π

4

π- 2Φ1

Explanation :
No Explanation available for this question

# A FM signal has a carrier swing of 100 kHz when modulating signal has a frequency of 8 kHz. The modulation index is

1.  6.25

2.  12.5

3.  7.5

4.  15

4

6.25

Explanation :
No Explanation available for this question

# In a step-graded p-n junction diode, what is the ratio of depletion region penetration depths into p and n regions (if the ratio of acceptor to donor impurity atoms densities is 1:2)

1.  2:1

2.  4:1

3.  1:2

4.  1:4

4

2:1

Explanation :
No Explanation available for this question

# A modulated signal f(t) is multiplied by another signal cos ωct yield f (t) cos2 ωc t. If f (t)↔ F (m), then f (t) to yield cos2 ωc t is

1.  F(ω)+F(ω-ωc)+F (ω-ωc)

2.  1/2 F(ω)+1/2[F(ω+ωc)+F (ω-ωc)

3.  1/2F(t)+1/2F(t)+cos 2ωct

4.  1/2 F(ω)+1/4[F(ω-2ωc)+F (ω+2ωc)

4