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EE314

Field Effect Transistors. IBM/Motorola Power PC620. Motorola MC68020. EE314. IBM Power PC 601. Construction of MOS NMOS and PMOS Types of MOS MOSFET Basic Operation Characteristics. Chapter 12: Field Effect Transistors. The MOS Transistor. Polysilicon. Aluminum.

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EE314

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  1. Field Effect Transistors IBM/Motorola Power PC620 Motorola MC68020 EE314 IBM Power PC 601

  2. Construction of MOS • NMOS and PMOS • Types of MOS • MOSFET Basic Operation • Characteristics Chapter 12: Field Effect Transistors

  3. The MOS Transistor Polysilicon Aluminum JFET – Junction Field Effect Transistor MOSFET - Metal Oxide Semiconductor Field Effect Transistor n-channel MOSFET (nMOS)& p-channel MOSFET (pMOS)

  4. Gate Oxide Gate Polysilicon Field-Oxide Source Drain (SiO ) 2 n+ n+ p+ stopper p-substrate Bulk Contact CROSS-SECTION of NMOS Transistor The MOS Transistor

  5. Gate | VGS | Source (of carriers) Drain (of carriers) Closed (on) (Gate = ‘1’) Open (off) (Gate = ‘0’) Ron | VGS | < | VT | | VGS | > | VT | Switch Model of NMOS Transistor

  6. Gate | VGS | Source (of carriers) Drain (of carriers) Closed (on) (Gate = ‘0’) Open (off) (Gate = ‘1’) Ron | VGS | > | VDD – | VT | | | VGS | < | VDD – |VT| | Switch Model of PMOS Transistor

  7. MOS transistors Symbols D D G G S Channel S Depletion NMOS Enhancement NMOS D D G G B S S NMOS with PMOS Enhancement Bulk Contact

  8. JFET and MOSFET Transistorsor Symbol L = 0.5-10 mm W = 0.5-500 mm SiO2 Thickness = 0.02-0.1 mm Device characteristics depend on L,W, Thickness, doping levels

  9. MOSFET Transistor Fabrication Steps

  10. Building A MOSFET Transistor Using Silicon http://micro.magnet.fsu.edu/electromag/java/transistor/index.html

  11. It is done. Now, how does it work?

  12. n-channel MOSFET Basic Operation Operation in the Cutoff region pn junction: reverse bias iD=0 for vGS<Vt0 Schematic When vGS=0 then iD=0 until vGS>Vt0 (Vt0 –threshold voltage)

  13. n-channel MOSFET Basic Operation Operation in the Triode Region For vDS<vGS-Vt0 and vGS>Vt0 the NMOS is operating in the triode region Resistor like characteristic (R between S & D, Used as voltage controlled R) For small vDS, iD is proportional to the excess voltagevGS-Vt0

  14. n-channel MOSFET Basic Operation Operation in the Triode Region Device parameter KP for NMOSFET is 50 mA/V2

  15. n-channel MOSFET Basic Operation Operation in the Saturation Region (vDS is increased) Tapering of the channel - increments of iD are smaller when vDS is larger When vGD=Vt0 then the channel thickness is 0 and

  16. n-channel MOSFET Basic Operation Example 12.1 An nMOS has W=160 mm, L=2 mm, KP= 50 mA/V2 and Vto=2 V. Plot the drain current characteristic vs drain to source voltage for vGS=3 V.

  17. n-channel MOSFET Basic Operation Example 12.1 Characteristic Channel length modulation id depends on vDS in saturation region (approx: iD =const in saturation region)

  18. p-channel MOSFET Basic Operation It is constructed by interchanging the n and p regions of n-channel MOSFET. Symbol Characteristic How does p-channel MOSFET operate? -voltage polarities -iD current -schematic

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