Physics : Semiconductor Electronics: Materials, Devices and Simple Circuits

In a common base amplifier, the phase difference between the input signal voltage and the output voltage is

• $\frac{\mathrm{\pi }}{4}$

• $\mathrm{\pi }$

• zero

• $\frac{\mathrm{\pi }}{2}$

The Fermi level of an intrinsic semiconductor is pinned at the centre of the bandgap. The probability of occupation of the highest electron state in valence band at room temperature will be

• zero

• between zero and half

• half

• one

The relation between amplification factor (μ), plate resistance (r_p) and mutual conductance (g_m) of a triode value is given by :

• $\mathrm{\mu } = {\mathrm{r}}_{\mathrm{p}} \times {\mathrm{g}}_{\mathrm{m}}$

• ${\mathrm{r}}_{\mathrm{p}} = \mathrm{\mu } \times {\mathrm{g}}_{\mathrm{m}}$

• ${\mathrm{g}}_{\mathrm{m}} = \mathrm{\mu } \times {\mathrm{r}}_{\mathrm{p}}$

• none of these

A light of wavelength 5000 Å falls on a sensitive plate with photoelectric work function 1.90 eV. The kinetic energy of the emitted photoelectrons will be :

(Given, h = 6.62 × 10^-34 Joule second)

• 0.1 eV

• 2 eV

• 0.581 eV

• 1.581

On applying a reverse bias to a junction diode, it:

• lowers the potential barrier

• raises the potential barrier

• increases the majority carrier current

• increases the minority carrier current

A n-type semiconductor is

• negatively charged

• positively charged

• neutral

• none of the above

Regarding a semiconductor which one of the following is wrong?

• There are no free electrons at room temperature

• There are no free electrons at 0K

• The number of free electrons increases with the rise of temperature

• The charge carriers are electrons and holes

Which of the following statements is true for an n-type semi-conductor?

• The donor level lies closely below the bottom of the conduction band

• The donor level lies closely above the top of the valence band

• The donor level lies at the halfway mark of the forbidden energy gap

• None of the above

When a p-n junction diode is connected to a battery with its p-side to positive terminal and n-side to negative terminal, the width of the depletion layer

• decreases

• increases

• first decreases then increases

• first increases then decreases

In forward and reverse biasing of a p-n junction diode, the ratio of resistances is

• 10² : 1 

• 10^-2 : 1 

• 1 : 10⁴

• 1 : 10^-4