96_exam2fall

96_exam2fall - YOUR NAME Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology 6.012 Electronic Devices

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YOUR NAME_______________________________ Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology 6.012 Electronic Devices and Circuits Exam No. 2 Notes: 1. Unless otherwise indicated, assume room temperature and that kT/q is 0.025 V. You may also approximate [(kT/q) ln 10] as 0.06 V. 2. Open book; 6.012 text and any other notes permitted. 3. All of your answers and any relevant work must appear on these pages. Any additional paper you hand in will not be graded. 4. Make reasonable approximations and assumptions. State and justify any such assumptions and approximations you do make. 5. Be careful to include the correct units with your answers when appropriate. 6. Be certain that you have all nine (9) pages of this exam booklet and make certain that you write your name at the top of this page in the space provided. 6.012 Staff Use Only PROBLEM 1 (36 maxium) PROBLEM 2 (28 maxium) PROBLEM 3 (36 maxium) TOTAL (100 maxium)
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Page 2 of 9 Problem 1 (36 points) This problem concerns the p-n junction diode illustrated below; it is not a silicon diode. Throughout this device , the minority carrier lifetime, min , is 10 -7 s; the electron mobility, µ e , is 3,600 cm 2 /V-s; the hole mobility, µ h , is 256 cm 2 /V-s; and the intrinsic carrier concentration at room temperature, n i (300K), is 10 5 cm -3 . The doping level on the p-side of the junction, N Ap , is 10 17 cm -3 and on the n-side, N Dn , it is 10 16 cm -3 . The cross-sectional area of the junction is 10 -4 cm 2 . n 10 cm 16 -3 p 10 cm 17 -3 A B + - v AB i D x (µm) -5 0 5 10 15 20 25 a) What are the relative magnitudes of the hole and electron currents at x = 0 when this device is forward biased? You may use the short base or long base approximation, which ever is appropriate, on either side of the junction (i.e., you should not have to use the complete sinh and cosh expressions). J
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This note was uploaded on 07/20/2009 for the course CSAIL 6.012 taught by Professor Prof.cliftonfonstadjr. during the Fall '03 term at MIT.

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96_exam2fall - YOUR NAME Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology 6.012 Electronic Devices

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