EE 121b - 4 - BJT

EE 121b - 4 - BJT - EE 121B Principles of Semiconductor...

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Slide 4-1 EE 121B – Chi On Chui EE 121B Principles of Semiconductor Device Design Bipolar Junction Transistors - I Professor Chi On Chui Electrical Engineering Department University of California, Los Angeles Email: chui@ee.ucla.edu
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Slide 4-2 EE 121B – Chi On Chui Outline Fundamentals of BJT Operation Amplification with BJTs Excess Carrier Distributions and Terminal Currents (Ch. 7)
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Slide 4-3 EE 121B – Chi On Chui Transistor Operation – Amplification and Switching A three-terminal non-linear device with a family of i D -v D curves, depending on the choice of v G Amplification – a large change in i D is obtained if an small ac signal is added to v G Switching – from i D = 0 to ~ E/R
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Slide 4-4 EE 121B – Chi On Chui Reverse Biased PN Junction with Carrier Generation The reverse current in PN junction depends on carrier generation near W EHP generation mechanisms Thermal excitation Optical excitation (e.g. hv > E g ) Electrical injection (i.e. minority carrier injection near W ) More EHP generation
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Slide 4-5 EE 121B – Chi On Chui Forward Biased PN Junction as a Carrier Injector The forward biased p + - n junction current is due mainly to holes injection ( Emitter Junction ) Sharing the same n region (called the Base , which is made “short”), the reverse biased p-n junction W CB collects the non-recombined , injected holes ( Collector Junction ) W CB
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Slide 4-6 EE 121B – Chi On Chui Hole and Electron Flows in a PNP Transistor The base current components include: i B1 – Electrons injection (diffusion) from B to E i B2 – Electrons recombination in B with injected holes from E i B3 – Electrons collection (drift) to B from C due to thermal generation p + ( E ) n ( B ) p ( C ) i Ep i Cp i En i B1 i B2 i B3 i Cn E B ( p + -n ) junction is forward biased C B ( p-n ) junction is reverse biased
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Slide 4-7 EE 121B – Chi On Chui Important Amplification Parameters in BJT – 1 Assumptions:
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This note was uploaded on 01/17/2012 for the course EE EE 110 taught by Professor Gupta during the Spring '09 term at UCLA.

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EE 121b - 4 - BJT - EE 121B Principles of Semiconductor...

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