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

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

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

 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. $2.25\; mV$

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

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