Electronic Devices and Circuits
Unit – 1 : Tutorial – 1 (14 July 2015)
Submission Date : 20th July 2015 (before 12:30 pm)
Short Questions:1. Explain why every semiconductor is electrically neutral in nature?
2. Define free electron, bound (valence) electron, hole, electron current and hole current in a semiconductor?
3. why intrinsic concentration of germanium is more than silicon at any temperature?
4. Why mobility of electron is more than mobility of hole in a semiconductor?
5. Justify : “Majority carriers in extrinsic semiconductor depends on doping concentration, while minority carriers depends on externally applied energy like temperature, light etc.. (but not on voltage)”.
Long Questions:1. Find the voltage required to move an electron from valence band to conduction bond?
2. Find the conductivity of intrinsic silicon at room temperature? If it is doped with phosphorous so that majority carrier concentration becomes 1016 donors/cm3. Find the conductivity of doped semiconductor? Give your comments from the results obtained.
3. An N type silicon bar 0.1 cm long and µm2 in cross sectional area has a majority carrier concentration of 5 x 1020 m-3 and the carrier mobility is 0.13 m2/V-sec at 300oK. If the charge of an electron is 1.6 x 10-19 coulomb. Find the resistance of the bar.
4. Define Mass Action Law and also find the minority carrier concentration of an n-type silicon, if it is doped with 1 phosphorous in every 1000 silicon atoms per cubic centimeter.
5. Find Minority carrier concentration of p-type silicon sample, whose resistivity is 1 kΩ-cm.
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