Presentation is loading. Please wait.

Presentation is loading. Please wait.

ECA1212 Introduction to Electrical & Electronics Engineering Chapter 6: Field Effect Transistor by Muhazam Mustapha, October 2011.

Similar presentations


Presentation on theme: "ECA1212 Introduction to Electrical & Electronics Engineering Chapter 6: Field Effect Transistor by Muhazam Mustapha, October 2011."— Presentation transcript:

1 ECA1212 Introduction to Electrical & Electronics Engineering Chapter 6: Field Effect Transistor by Muhazam Mustapha, October 2011

2 Learning Outcome Be able to explain some basic physical theory and operation of FET Be able to do calculation on DC and AC analysis on FET circuit By the end of this chapter students are expected to:

3 Chapter Content Theory of FET FET Operation FET in Digital Circuit

4 Field Effect Transistor CO1

5 Field Effect Transistor FET is a piece of electronic device that conducts electricity by the control of a gate It can be considered as a voltage controlled resistor or voltage controlled current source Gate Current flows through the center body of channel from terminals called drain to source Gate is a plate not touching the substrate Drain Source Channel CO1

6 FET Types There are many types of FET –MOSFET – Metal Oxide Semiconductor FET –JFET – Junction FET –NMOS – n-channel MOSFET –PMOS – p-channel MOSFET We will cover mostly NMOS CO1

7 Channel Types FET is also characterized by its channel n-channel –The majority carrier in the channel is electron p-channel –The majority carrier in the channel is hole CO1

8 Modes Enhancement mode –FET is normally NOT conducting current even when given voltage at drain and source –Gate is to increase the current Depletion mode –FET is normally conducting current when given voltage at drain and source –Gate is to decrease the current CO1

9 Depletion Mode Drain Source Gate p-channel –Current flow is reduced by putting a positive voltage at gate to repel holes flow and finally block the current –The more positive the gate, the less current flow +ve ve p-channel Hole Flow Gates electric field repelling holes +ve CO1

10 Depletion Mode Drain Source Gate n-channel –Current flow is reduced by putting a negative voltage at gate to repel electrons flow and finally block the current –The more negative the gate, the less current flow +ve ve n-channel Electron Flow Gates electric field repelling electrons ve CO1

11 Enhancement Mode (PMOS) Drain Source Gate p-channel –When negative voltage is put to drain that is made of highly p dopant (p + ), reverse bias junction is formed at drain – hence no current flows –Negative voltage is put to gate to attract holes and effectively compensate the reverse biases – until current can flow ve +ve n-substrate Gates electric field attracting holes p-channel formation p+p+ ve p+p+ Hole Flow CO1

12 Enhancement Mode (NMOS) Drain Source Gate n-channel –When positive voltage is put to drain that is made of highly n dopant (n + ), reverse bias junction is formed at drain – hence no current flows –Positive voltage is put to gate to attract electrons and effectively compensate the reverse biases – until current can flow +ve ve p-substrate Gates electric field attracting electrons n-channel formation n+n+ +ve n+n+ Electron Flow CO1

13 Circuit Symbol and Notations n-channel p-channel DepletionEnhancementJFET CO1

14 Operation Region CO1

15 I-V Characteristic Ohmic Region V GS = 5.0V V GS = 4.5V V GS = 4.0V V GS = 3.5V V GS = 3.0V V GS = 2.5V I D, mA Saturation Region Cutoff Region V DS, V CO1

16 Operation Region Cutoff –V GS < V T and V GD < V T –No current flow Ohmic / Triode –V GS > V T and V GD > V T –Linear I-V characteristic CO1

17 Operation Region Saturation –V GS > V T and V GD < V T –I D is controlled by V GS (Saturation Region Formula): Conductance parameter Threshold voltage – minimum voltage to form a conducting channel CO1

18 FET In Digital Circuit CO1

19 NAND, NOR and NOT Gates CO1


Download ppt "ECA1212 Introduction to Electrical & Electronics Engineering Chapter 6: Field Effect Transistor by Muhazam Mustapha, October 2011."

Similar presentations


Ads by Google