1. Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc/
EE Semiconductor Electronics Design Project Spring Lecture 07
Professor Ronald L. Carter
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2. Lab schedule
As announced last week, plan to attend your lab session (Tu or Th at 230 to 500 PM) this week for additional Cadence instruction.
Topics to be covered
schematic capture of a circuit
making a symbol
simulating a circuit
L07 February 05

3. Bipolar junction transistor (BJT)
General bias on a pnp transistor
The BJT is a ‘silicon sandwich’ p+np- or n+pn-
npn For. Active BJT action when VBE > 0 and VBC < 0 p n E B C
VEB
VCB
Charge neutral Region
Depletion Region
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4. 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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5. Ebers-Moll (npn injection model)
(common-emitter) E
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6. E-M model equations
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7. Ebers-Moll Model (npn bipolar jctn. tran. w/o inj.)
aRIR
aFIF E C
(Common base) B
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8. IC npn BJT (*Fig 9.2a)
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9. npn BJT regions of operation
VBC
Reverse Active
Saturation
VBE
Forward Active
Cutoff
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10. npn FA BJT minority carrier distribution (Fig 9.4*)
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11. npn RA BJT minority carrier distribution (Fig 9.11a*)
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12. npn cutoff BJT min carrier distribution (Fig 9.10a*)
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13. npn sat BJT minority carrier distribution (Fig 9.10b*)
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14. Defining currents in FA mode npn BJT (Fig 9.13*)
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15. 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 for NE --> density of states at cond. band. edge
Junction breakdown at BC junction
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16. npn Base-width modulation (Early Effect)
Fig 9.15*
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17. Base-width modulation (Early Effect, cont.)
Fig 9.16*
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18. Emitter current crowding in base
Fig 9.21*
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19. Interdigitated base fixes emitter crowding
Fig 9.23*
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20. Effect of HLI in npn base region
Figs 9.18 and 9.19*
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21. Ebers-Moll Model (Neglecting G-R curr)
(Fig. 9.30*)
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22. Hybrid-pi Circuit model
Fig 9.33 Semiconductor Physics and Devices, 2nd ed., by Neamen, Irwin, Boston, 1997.
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23. Hybrid-pi circuit model
Adapted from inj. model version of E-M model with parasitic rb, rc, re, and CSubst
C-E branch is linking current
B-E branch is the reduced B-E diode with diffusion (for and rev) resistance and capacitance and junction cap.
B-C branch is the reduced B-C diode with diffusion (for and rev) resistance and capacitance and junction cap.
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24. References
* Semiconductor Physics & Devices, by Donald A. Neamen, Irwin, Chicago, 1997.
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