1. EE 5340 Semiconductor Device Theory Lecture 29 - Fall 2010
Professor Ronald L. Carter

2. Final Exam EE 5340 Section 001 The Final is comprehensive
11:00 AM to 1:30 PM
Wednesday, December 15 in
108 NH
Cover sheet will be posted on web page at
The Final is comprehensive
20% to 25% on Test 1 material
20% to 25% on Test 2 material
Balance of final on material since Test 2
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3. Junction Field-Effect Transistor (JFET)
Based on figure 12.18*
n-type channel
Active channel height, a L
Ch to Substr D.R.
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4. Pinch-off Voltage Note: In depl mode devices, Vp0 > Vbi
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5. Channel conductance and drain current
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6. N-ch. ohmic reg drain current soln.
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7. Saturation drain current,
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8. Ideal JFET drain characteristics
Ohmic, ID1
Saturated: ID,sat ~ID1,sat ID
ID,sat
Non-physical analytic extension of ID1
VDS,sat
VDS
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9. n-channel JFET gate characteristicID
Saturated: ID,sat, approx.
IDSS
Saturated: ID1,sat Vp
VGS
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10. Small-signal para- meters: gds and gd
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11. Graphical interpre- tation of gds and gdID
ID,sat
Slope = gds
Slope = gd
VDS,sat
VDS
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12. Small-signal gain params: gmL and gms
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13. Channel Modulation Capacitances
Based on figure 12.18*
n-type channel
Active channel height, a L
Ch to Substr D.R.
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14. Application of JFET theory to MESFET
The channel material is often GaAs
The substrate is often semi-insulating gallium arsenide (SI GaAs)
Vbi is replaced by Vnbi, the band-bending in the semiconductor
Often limited by surface state pinning and not determined exactly by cs
Neff is now exactly Nch
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15. References
* Semiconductor Physics & Devices, by Donald A. Neamen, Irwin, Chicago, 1997.
**Device Electronics for Integrated Circuits, 2nd ed., by Richard S. Muller and Theodore I. Kamins, John Wiley and Sons, New York, 1986
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