EE 5340 Semiconductor Device Theory Lecture 29 - Fall 2010 Professor Ronald L. Carter ronc@uta.edu http://www.uta.edu/ronc

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 http://www.uta.edu/ronc/5340/tests/ 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 L29 06Dec2010

Junction Field-Effect Transistor (JFET) Based on figure 12.18* n-type channel Active channel height, a L Ch to Substr D.R. L29 06Dec2010

Pinch-off Voltage Note: In depl mode devices, Vp0 > Vbi L29 06Dec2010

Channel conductance and drain current L29 06Dec2010

N-ch. ohmic reg drain current soln. L29 06Dec2010

Saturation drain current, L29 06Dec2010

Ideal JFET drain characteristics Ohmic, ID1 Saturated: ID,sat ~ID1,sat ID ID,sat Non-physical analytic extension of ID1 VDS,sat VDS L29 06Dec2010

n-channel JFET gate characteristic ID Saturated: ID,sat, approx. IDSS Saturated: ID1,sat Vp VGS L29 06Dec2010

Small-signal para- meters: gds and gd L29 06Dec2010

Graphical interpre- tation of gds and gd ID ID,sat Slope = gds Slope = gd VDS,sat VDS L29 06Dec2010

Small-signal gain params: gmL and gms L29 06Dec2010

Channel Modulation Capacitances Based on figure 12.18* n-type channel Active channel height, a L Ch to Substr D.R. L29 06Dec2010

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 L29 06Dec2010

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 L29 06Dec2010