ch06 - Fundamentals of Microelectronics CH1 CH2 CH3 CH4 CH5...

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1 Fundamentals of Microelectronics CH1 Why Microelectronics? CH2 Basic Physics of Semiconductors CH3 Diode Circuits CH4 Physics of Bipolar Transistors CH5 Bipolar Amplifiers CH6 Physics of MOS Transistors CH7 CMOS Amplifiers CH8 Operational Amplifier As A Black Box
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2 Chapter 6 Physics of MOS Transistors 6.1 Structure of MOSFET 6.2 Operation of MOSFET 6.3 MOS Device Models 6.4 PMOS Transistor 6.5 CMOS Technology 6.6 Comparison of Bipolar and CMOS Devices
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CH 6 Physics of MOS Transistors 3 Chapter Outline
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CH 6 Physics of MOS Transistors 4 Metal-Oxide-Semiconductor (MOS) Capacitor The MOS structure can be thought of as a parallel-plate capacitor, with the top plate being the positive plate, oxide being the dielectric, and Si substrate being the negative plate. (We are assuming P-substrate.)
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CH 6 Physics of MOS Transistors 5 Structure and Symbol of MOSFET This device is symmetric, so either of the n+ regions can be source or drain.
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CH 6 Physics of MOS Transistors 6 State of the Art MOSFET Structure The gate is formed by polysilicon, and the insulator by Silicon dioxide.
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CH 6 Physics of MOS Transistors 7 Formation of Channel First, the holes are repelled by the positive gate voltage, leaving behind negative ions and forming a depletion region. Next, electrons are attracted to the interface, creating a channel (“inversion layer”).
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CH 6 Physics of MOS Transistors 8 Voltage-Dependent Resistor The inversion channel of a MOSFET can be seen as a resistor. Since the charge density inside the channel depends on the gate voltage, this resistance is also voltage-dependent.
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CH 6 Physics of MOS Transistors 9 Voltage-Controlled Attenuator As the gate voltage decreases, the output drops because the channel resistance increases. This type of gain control finds application in cell phones to avoid saturation near base stations.
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Physics of MOS Transistors 10 MOSFET Characteristics The MOS characteristics are measured by varying V G while keeping V D constant, and varying V D while keeping V G constant. (d) shows the voltage dependence of channel resistance.
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ch06 - Fundamentals of Microelectronics CH1 CH2 CH3 CH4 CH5...

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