Practice Questions on Electronic Devices

Q1.

For a given 50 W energy vapour lamp $ 0.1\% $ of the electric energy supplied to the lamp, appears 
in the ultraviolet line 2,537 A$ ^\circ $. The number of photons per second, of this wavelength emitted by the lamp is:

A.

$ 4.7\times 10^{15}\text{ photons/sec}     $

B.

$ 6.4\times 10^{16}\text{ photons/sec}     $

C.

$ 7.8\times 10^{17}\text{ photons/sec}     $

D.

$ 8.5\times 10^{19}\text{ photons/sec}     $

 View Ans

Q2.

What is the maximum doping concentration in the n-region of uniformly doped silicon $p^+n$ junction if the reverse bias voltage of $10\text V$ is applied? Given the electric field is limited to $\text E_{max}=10^6$ V/cm. 

A.

$3.2\times 10^{19} cm^{-3}$

B.

$3.2\times 10^{17} cm^{-3}$

C.

$6.4\times 10^{17} cm^{-3}$

D.

$6.4\times 10^{19} cm^{-3}$

 View Ans

Q3.

A Si sample with $ n_{no}=10^{14}\;\text {cm}^{-3} $ is illuminated with light and $ 10^{13} $ electron-hole pairs/$ \text{cm}^3 $ are created every microsecond. If $ \tau_{n}=\tau_{p}=2\;\mu \text s$. The minority concentration is:

A.

$ 0.5\times 10^{13}\;\text{cm}^{-3} $

B.

$ 1\times 10^{11}\;\text{cm}^{-3} $

C.

$ 2\times 10^{13}\;\text{cm}^{-3} $ 

D.

$ 3\times 10^{10}\;\text{cm}^{-3} $

 View Ans

Q4.

A sample Si is doped with $ 10^{16}$ phosphorous $ \text{atoms}/\text{cm}^3 $. Find the Hall voltage (in mV) in a sample with $ \text W=500\;\mu \text m $, $ \text A=2.5\times 10^{-3}\text{ cm}^2 $, $ \text I=1\text { mA} $ and $ \text B_{z}=10^{-4}\text { Wb}/\text{cm}^2 $.

A.

$-1.25\; mV$

B.

$0.55\; mV$

C.

$1.15 \;mV$

D.

$2.25\; mV$

 View Ans

Q5.

For a silicon linearly graded junction with a impurity gradient $ 10^{20}\text { cm}^{-4} $, depletion width is $ 0.5\;\mu \text m $. The maximum field is:

A.

$ 7.50\times 10^3\text V/\text{cm} $

B.

$ 4.75\times 10^3\text V/\text{cm} $

C.

$3.05\times 10^3\text V/\text{cm}  $

D.

$ 2.75\times 10^3\text V/\text{cm} $

 View Ans


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