1. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/
Semiconductor Device Modeling and Characterization – EE5342 Lecture 20 – Spring 2011
Professor Ronald L. Carter

2. IC npn BJT (*Fig 9.2a)
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3. npn BJT currents (F A region, ©RLC)
IC = JCAC
IB=-(IE+IC )
JnE
JnC
IE =
-JEAE
JRB=JnE-JnC
JpE
JGC
JRE
JpC
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4. Defining currents in FA mode npn BJT (Fig 9.13*)
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5. Common base current gain, aF (cont.)
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6. Common emitter current gain, bF
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7. Ebers-Moll Model (Neglecting G-R curr)
(Fig. 9.30*)
-JEAE=IE
JCAC=IC
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8. Source of Ebers-Moll Equations (E)
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9. Source of Ebers-Moll Equations (C)
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10. E-M model equations
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11. Ebers-Moll Model (Neglecting G-R curr)
(Fig. 9.30*)
-JEAE=IE
JCAC=IC
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12. Linking current E-M circuit model
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13. Linking current version of E-M model
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14. Linking current E-M model (cont)
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15. Non-ideal effects in BJTs
Recombination/Generation effects
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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16. Recombination/Gen Currents (FA)
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17. npn Base-width mod. (Early Effect)
Fig 9.15*
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18. References
1 OrCAD PSpice A/D Manual, Version 9.1, November, 1999, OrCAD, Inc.
2 Semiconductor Device Modeling with SPICE, 2nd ed., by Massobrio and Antognetti, McGraw Hill, NY, 1993.
* Semiconductor Physics & Devices, by Donald A. Neamen, Irwin, Chicago, 1997.
** Modeling the Bipolar Transistor, by Ian Getreau, Tektronix, Inc., (out of print).
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