html5-img
1 / 23

Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader

Lecture 10. Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET). Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader. By: Dr Tarek Abdolkader. OUTLINE.

celestyn-leighton
Download Presentation

Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 10 Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader By: Dr Tarek Abdolkader

  2. OUTLINE • At the end of this lecture, the student should be able to: • Describe the construction of Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) • Differentiate between Enhancement and Depletion MOSFETs and their symbols • Explain the operation of D-MOSFET and E-MOSFET • Demonstrate D-MOSFET and E-MOSFET characteristics • Define the different parameters of MOSFET • Describe the different methods of MOSFET biasing Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  3. MOSFET CONSTRUCTION • There are basically two types of MOSFETs: Depletion-type MOSFET (D-MOSFET) and Enhancement-type MOSFET(E-MOSFET) Depletion-type MOSFET (D-MOSFET) Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Enhancement-type MOSFET (E-MOSFET) Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  4. MOSFET CONSTRUCTION AND SYMBOLS D-MOSFET Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  5. MOSFET CONSTRUCTION AND SYMBOLS E-MOSFET Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  6. D- MOSFET CHARACTERISTICS Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  7. D- MOSFET CHARACTERISTICS A D-MOSFET has parameters of VGS(off)= -6V and IDSS = 1 mA. Plot the transconductance curve for the device. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  8. D- MOSFET CHARACTERISTICS • D-MOSFET is very similar to JFET: • In D-MOSFET no gate current at all because of the insulator between gate and channel • If VGS < 0, both devices have the same characteristics. • For VGS > 0, JFET cannot be used. However, D-MOSFET can be used with drain currents larger than IDSS. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • n-channel D-MOSFET with VGS < 0, is said to be in Depletion mode, while n-channel D-MOSFET with VGS > 0, is said to be in Enhancement mode Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  9. D- MOSFET CHARACTERISTICS n-channel p-channel Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • More positive VGS depletes more holes from the p-channel and decrease its conductivity. So, higher VGS leads to less drain current. • VGS(off) for p-channel D-MOSFET is positive • More negative VGS attracts more holes to the p-channel and increase its conductivity. So, lower VGS leads to more drain current. • More negative VGS depletes more electrons from the n-channel and decrease its conductivity. So, lower VGS leads to less drain current. • VGS(off) for n-channel D-MOSFET is negative • More positive VGS attracts more electrons to the n-channel and increase its conductivity. So, higher VGSleads to more drain current. Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  10. D- MOSFET CHARACTERISTICS For a certain D-MOSFET, IDSS = 10 mA and VGS(off) = ‒ 8 V. (a) Is this an n-channel or a p-channel? (b) Calculate ID at VGS = ‒3 V. (c) Calculate ID at VGS = +3 V. Example Solution Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  11. E- MOSFET CHARACTERISTICS • There is no built-in channel in E-MOSFET. • A positive gate bias has to be applied on the n-channel. • Minimum value of VGS needed to form the n-channel and passes drain current is called “threshold voltage Vth“ Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  12. E- MOSFET CHARACTERISTICS Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  13. E- MOSFET CHARACTERISTICS n-channel p-channel Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • Vth for p-channel E-MOSFET is negative • Vth for n-channel E-MOSFET is positive Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  14. E- MOSFET CHARACTERISTICS Example For a 2N7002 E-MOSFET, ID(on) = 500 mA (for a point well above the threshold voltage) at VGS = 10 V and VGS(th) = 1 V. Determine the drain current for VGS = 5 V. Solution Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  15. MOSFET BIASING D-MOSFET • D-MOSFET can be operated with either positive or negative gate bias (VGS). • A simple method is to set VGS = 0. • RG is used for protecting ac signal input from being shorted • Remember that at VGS = 0, the drain current ID = IDSS Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • Remember that for JFET, there was a resistance RS at the source terminal to make VGS negative. Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  16. MOSFET BIASING Example Determine the drain-to-source voltage in the circuit shown. IDSS = 12 mA and VGS(off) = ‒8 V. Solution Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  17. MOSFET BIASING E-MOSFET • For E-MOSFET, VGSmust be greater than threshold voltage VGS(th). So, zero bias cannot be used. • Two methods of biasing are shown: (a) voltage-divider bias, (b) Drain-feedback bias. • Note that here also RS is not used because it will raise the potential of source terminal and decrease VGS. In BJT, we were using RE to increase the input impedance Zin but here we do not need it because Zin is already high Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  18. MOSFET BIASING Example Determine VGS and VDS for the E-MOSFET circuit shown. Assume that ID(on)= 200 mA at VGS = 4 V and VGS(th)= 2 V. Solution Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  19. MOSFET BIASING Example Determine the values of ID and VDSfor the circuit shown. The data sheet for this particular MOSFET gives ID(on) = 10 mA when VGS = VDS Solution Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  20. FET AC analysis Graphical Picture • Change in VGS around the VGSQ leads to change in ID around IDQ • We use the symbol Vgs , Id , … for the change in VGS , ID , … around the Q point (ac components) • The transconductance: Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  21. FET AC analysis Equivalent Circuit • In ac analysis we replace the transistor by its equivalent circuit: Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • (a) Complete equivalent circuit (b) Simplified equivalent circuit • rgs represents the resistance between gate and source which is infinitely large • rdsrepresents the dependence of drain current on drain to source voltage which is very small. • Although the dc resistance of channel RDS = IDQ/VDSQ is small, the ac resistance rds is very high Electronic devices (802311) Lecture 10 Dr Tarek Abdolkader

  22. General Knowledge Electrostatic Discharge • Excess static charge may be accumulated on the gate of a MOSFET. • All MOS devices are subject to damage due to Electro-Static Discharge (ESD) Humans don't feel ESD transfers less than 3,500 volts, but MOS devices are sensitive to charges at less than half of this level. So, when you work on MOS devices, you may damage the components in the computer via ESD, and not even feel it. Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader • MOSFETs are usually shipped in conductive foam. • MOSFETs are usually shipped with a wire ring around the leads, which is removed just prior to installing the MOSFET in a circuit. • All instruments and metal benches used in assembly or testing of MOSFETs should be connected to earth ground. • Handler’s rest should be connected to a grounding strap Electronic Circuits (802312) Lecture 5 Dr Tarek Abdolkader

  23. General Knowledge MOSFET scaling Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Dr Tarek Abdolkader Electronic Circuits (802312) Lecture 5 Dr Tarek Abdolkader

More Related