Electronic Devices Chapter-Wise Test 6

Correct answer Carries: 4.

Wrong Answer Carries: -1.

In a full-wave rectifier, the voltage across each diode is:

In a centre-tap full-wave rectifier, each diode rectifies half the total secondary voltage, as the centre tap splits the AC input into two equal halves.

Full secondary voltage
Twice the secondary voltage
Zero voltage
Half the secondary voltage
4

Which of the following has the highest energy gap?

Energy gaps: C (diamond) = 5.4 eV, Si = 1.1 eV, Ge = 0.7 eV, Sn = 0 eV (metal). Carbon has the highest energy gap among these, making it an insulator.

Si
Ge
Sn
C
4

The majority carriers in a p-type semiconductor are:

In a p-type semiconductor, trivalent doping creates holes as majority carriers, while electrons are minority carriers (\( n_h \gg n_e \)).

Electrons
Negative ions
Positive ions
Holes
4

A Si crystal with \( 5 \times 10^{28} \, \text{atoms} \, \text{m}^{-3} \) is doped with 0.5 ppm of pentavalent impurity. The number of donor electrons per cubic meter is:

0.5 ppm = \( 0.5 \times 10^{-6} \). Number of donor atoms = \( 0.5 \times 10^{-6} \times 5 \times 10^{28} = 2.5 \times 10^{22} \, \text{m}^{-3} \), each contributing one electron.

\( 5 \times 10^{22} \, \text{m}^{-3} \)
\( 1 \times 10^{22} \, \text{m}^{-3} \)
\( 7.5 \times 10^{22} \, \text{m}^{-3} \)
\( 2.5 \times 10^{22} \, \text{m}^{-3} \)
4

In an extrinsic semiconductor, the minority carrier concentration is reduced due to:

Doping increases majority carriers (electrons in n-type, holes in p-type), enhancing recombination with minority carriers, thus reducing their concentration indirectly.

Increased recombination
Thermal generation
Diffusion process
Drift current
1

The space-charge region in a p-n junction is also known as:

The space-charge region, formed by immobile ionized impurities after carrier diffusion, is called the depletion region due to the absence of free charge carriers.

Diffusion zone
Conduction zone
Depletion region
Neutral region
3

The reverse bias resistance of a p-n junction diode is typically:

In reverse bias, the diode allows only a small reverse saturation current (\( \mu \text{A} \)), resulting in a very high resistance compared to the low resistance in forward bias.

Low
Moderate
Zero
High
4

The voltage drop in a forward-biased diode occurs mainly across:

In forward bias, the applied voltage mostly drops across the depletion region due to its high resistance, with negligible drops across the p-side and n-side.

P-side
Depletion region
N-side
Entire diode
2

What is the primary source of charge carriers in an intrinsic semiconductor at room temperature?

In an intrinsic semiconductor, charge carriers (electrons and holes) are generated by thermal excitation at temperatures above 0 K, breaking covalent bonds and creating electron-hole pairs.

Thermal excitation
Doping impurities
External electric field
Light absorption
1

The forward bias current in a diode is typically measured in:

In forward bias, the current due to majority carrier diffusion is large, typically in the milliampere (mA) range, requiring a milliammeter for measurement.

Microampere (\( \mu \text{A} \))
Nanoampere (nA)
Milliampere (mA)
Ampere (A)
3

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