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EE 121b - HW 2

# EE 121b - HW 2 - collector-base depletion regions 2 When a...

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EE 121B / Winter 2009 / Prof. Chui Homework #02, p.1 EE 121B Principles of Semiconductor Device Design Winter 2009 Homework #02 (Due Date: Jan 30 th , 2009, 12 pm in Boelter 6731) Apply the same set of physical constants and general assumptions as in Homework #01. Questions: 1) For the NPN BJT shown in Fig. 1 that is maintained under equilibrium, a) Sketch as a function of position inside the BJT: i) The energy band diagram together with the Fermi level positions, ii) The electrostatic potential, setting V = 0 in the emitter region, iii) The electric field, and iv) The charge density b) Calculate the potential difference between the collector and emitter c) Determine the neutral base width W b d) Calculate the maximum magnitude of the electric fields in the emitter-base and
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Unformatted text preview: collector-base depletion regions 2) When a 0.5 V forward bias and 10.0 V reverse bias are respectively applied across the emitter-base and collector-base junctions, a) Plot the excess carrier density in the base region b) Calculate: i) The emitter injection efficiency, ii) The base transport factor, iii) The common base current gain, and iv) The common emitter current gain c) Repeat a) and b) if the minority carrier lifetime in the base becomes 10-9 s; Identify and explain any difference(s) observed N ( N dE ) P ( N aB ) W Base N ( N dc ) W b Figure 1 Emitter Base Collector Width, W Base ( µ m) 3 Doping (cm-3 ) 5 × 10 18 10 16 10 15 Minority Carrier Lifetime (s) 5 × 10-8 2.5 × 10-7 2 × 10-6 Minority Carrier Mobility (cm 2 /V-s) 130 600 800...
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