Digital ic 2 device outline pn junction principle

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Digital IC 2: Device outline PN junction principle CMOS transistor introduction Ideal I-V characteristics under static conditions Dynamic Characteristics Nonideal I-V effects 26/74
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Digital IC 2: Device What is a Transistor? V GS V T R on S D A Switch! |V GS | An MOS Transistor 27/74
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Digital IC 2: Device Why MOS transistor? MOS Metal Oxide Semiconductor type Field Effective Transistor-MOSTFET) Merits Simple manufacturing process yield Low power, high density High input resistor 28/74
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Digital IC 2: Device Terminal Voltages Mode of operation depends on Vgs, Vgd, Vds V ds = V d V s = V gs - V gd Source and drain are symmetric diffusion terminals source is terminal at lower voltage Hence V ds 0 nMOS body is grounded. First assume source is 0 too. Three regions of operation Cutoff Linear Saturation V g V s V d V gd V gs V ds + - + - + - 29/74
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Digital IC 2: Device nMOS Cutoff No channel I ds = 0 + - V gs = 0 n+ n+ + - V gd p-type body b g s d 30/74
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Digital IC 2: Device nMOS threshold voltage V t >V gs >0 depletion region(inversion) is formed below the gate V gs =V t A strong inversion is built up, the potential at the silicon surface reaches a critical value Further increases the gate voltage produce no further changes in the depletion layer width 31/74
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