Chapter 5FET1 - /2/12 . Chapter 5 Field-Effect Transistors...

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S J T U J. C h e n 1 3/2/12 Chapter 5 Field-Effect Transistors (FETs)
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3/2/12 SJTU J. Chen 2 Content Physical operation and current-voltage cha racteristics DC analysis Biasing in MOS amplifier circuit and basic configuration
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S J T U J. C h e n 3/2/12 Physical operation and current -voltage characteristic s
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3/2/12 SJTU J. Chen 4 FET: Field Effect Transistor There are two types MOSFET: metal-oxide-semiconductor FET JFET: Junction FET MOSFET is also called the insulated-gate FET or I GFET. Quite small Simple manufacturing process Low power consumption Widely used in VLSI circuits( >800 million on a single IC chip) Introduction to FET
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3/2/12 SJTU J. Chen 5 Device structure of MOSFET ( n -type) p -type S emiconductor Substrate (Body) Body(B) n + n + O xide (SiO2) Source(S) Gate(G) Drain(D) M etal l For normal operation, it is needed to create a conducting channel between Source and Drain Channel area
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3/2/12 SJTU J. Chen 6 Ø An n channel can be induced at the top of the substrate beneath the gate by applying a positive voltage to the gate Ø The channel is an inversion layer Ø The value of VGS at which a sufficient number of mobile electrons accumulate to form a conducting channel is called the threshold voltage ( Vt ) Creating a channel for current fl ow
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3/2/12 SJTU J. Chen 7 Ø L = 0.1 to 3 μ m Ø W = 0.2 to 100 μ m Ø Tox= 2 to 50 nm Device structure of MOSFET ( n -type) Cross-section view
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3/2/12 SJTU J. Chen 8 According to the type of the channel , FETs ca n be classified as MOSFET § N channel § P channel JFET § P channel § N channel Classification of FET Enhancement type Depletion type Enhancement type Depletion type
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3/2/12 SJTU J. Chen 9 Drain current under small voltage vDS Ø An NMOS transistor with vGS > Vt and with a small vDS applied. -
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This note was uploaded on 03/02/2012 for the course EI 207 taught by Professor Chengjianping during the Fall '10 term at Shanghai Jiao Tong University.

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Chapter 5FET1 - /2/12 . Chapter 5 Field-Effect Transistors...

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