midterm 2 sample (2011) solution

midterm 2 sample (2011) solution - Midterm Exam 2 makeup...

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Midterm Exam 2 makeup (solution) ECE103 2/27/09 1. (40 points). Define the following terms concisely, (i) Space charge region, (ii) Avalanche breakdown, (iii) Ideality factor (n or η), (iv)Transistor action, (v) Emitter efficiency, (vi) Base transport coefficient. (vii) LED efficiency, (viii) solar cell fill factor and power efficiency. Space charge region: Is the region on either side of the metallurgical junction in which there is a net charge density due to positively charged ionized donors in the n-region and negatively charged ionized acceptors in the p-region. Avalanche breakdown: A process in which a large reverse bias current across a pn junction is induced. Electrons generated in the depletion region or within one diffusion length from the diffusion region are accelerated in the large electric field in a reverse biased junction, gain large kinetic energy and collide with the crystal atoms in the depletion region and ionize electrons from the valence band to the conduction band causing generation of electron-hole pairs. The new generated electrons and holes will undergo the same process, and excessive amount of current flow through the junction. Ideality factor (n or η): Is a measure of how closely the diode current follows the ideal diode equation by adding it to the denominator of the exponential factor in the diode equation. In the ideal diode equation under forward bias, η=1 because the current is diffusion dominated. If the recombination current is dominant, η=2. Transistor action:
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This note was uploaded on 04/02/2011 for the course ECE 103 taught by Professor Song during the Spring '11 term at UCSB.

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midterm 2 sample (2011) solution - Midterm Exam 2 makeup...

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