1. EE 5340 Semiconductor Device Theory Lecture 19 – Spring 2011
Professor Ronald L. Carter

2. Test 2 – Tuesday 05Apr11 11 AM Room 129 ERB Covering Lectures 11 to19
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3. npn BJT currents in the forward active region ©RLC
IC = JCAC
IB=-(IE+IC )
JnE
JnC
IE =
-JEAE
JRB=JnE-JnC
JpE
JGC
JRE
JpC
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4. E current equations mode npn BJT (w/o gen/rec)
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5. C current equations in npn BJT (w/o gen/rec)
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6. Ebers-Moll Model (Neglecting G-R curr)
(Fig. 9.30*)
-JEAE=IE
JCAC=IC
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7. Source of Ebers-Moll Equations (E)
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8. Source of Ebers-Moll Equations (C)
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9. E-M model equations
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10. Ebers-Moll Model (Neglecting G-R curr)
Fig. 9.30*
aFIF
aRIR
-JEAE
= IE
JCAC
= IC E C B
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11. E-M linking current model
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12. E-M linking current model (cont)
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13. E-M linking current model (cont)
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14. More non-ideal effects in BJTs
Base-width modulation (FA: xB changes with changes in VBC)
Current crowding in 2-dim base
High-level injection (minority carriers g.t. dopant - especially in the base).
Emitter Bandgap narrowing (NE ~ density of states at cond. band. edge)
Junction breakdown at BC junction
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15. Recombination/Generation Currents (FA)
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16. FA npn figure of merit – emitter efficiency
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17. FA npn figure of merit – base transport factor
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18. FA npn figure of merit – recombination factor
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19. Common base current gain, aFaT d
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20. Common base current gain, aF (continued)
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21. Common emitter current gain, bF
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22. Common base current gain, aF (cont.)
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23. Common emitter current gain, bF
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24. References
* Semiconductor Physics and Devices, 2nd ed., by Neamen, Irwin, Boston, 1997.
**Device Electronics for Integrated Circuits, 2nd ed., by Muller and Kamins, John Wiley, New York, 1986.
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