Lecture2

Lecture2 - ECE ECE 124A VLSI Principles Lecture 2 Prof...

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ECE 124A LSI Principles VLSI Principles ecture 2 Lecture 2 Prof. Kaustav Banerjee Electrical and Computer Engineering E-mail: [email protected] @ Kaustav Banerjee Lecture 2, ECE 124A, VLSI Principles
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BJT vs FETs Js s Both are based on basic properties of pn junctions A Bipolar Junction Transistor (BJT) is a 3 terminal device Uses the injection of minority carriers (under a forward bias) BJTisa “bipolar” device (both electrons are holes are involved A BJT is a bipolar device (both electrons are holes are involved in its operation) It is an asymmetric device….why? Field Effect Transistor (FET) is also a 3 terminal device (plus a A Field Effect Transistor (FET) is also a 3 terminal device (plus a substrate terminal) A FET is a “unipolar” device (majority carrier only) is based on controlling the depletion width of a--- nction It is based on controlling the depletion width of a junction (JFET) or a Schottky Barrier (MESFET) through a control (gate) voltage ower has been the main driver for various technologies vacuum Kaustav Banerjee Lecture 2, ECE 124A, VLSI Principles 2 Power has been the main driver for various technologies …..vacuum tubes, BJT, PMOS, NMOS, CMOS…. .???
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Recalling the BJT…. . Schematic cross-sectional view of a planar NPN bipolar junction transistor …emitter is more heavily doped than chematic symbols for Basic structure of an NPN BJT collector ….depth of “p” region must be smaller than the diffusion length of electrons Schematic symbols for PNP and NPN type BJTs Both electrons and holes are involved in the operation…. .hence the name “bipolar” For NPN BJT: electrons are injected from a high-concentration emitter (n++) into the pe base where they are minority carriers that diffuse toward the collector Kaustav Banerjee Lecture 2, ECE 124A, VLSI Principles 3 p-type base…. .where they are minority carriers that diffuse toward the collector (n+)…. .hence BJTs are minority-carrier devices
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ther FETs Other FETs…. . If the metal gate electrode is separated from the emiconductor by an insulator etal sulator semiconductor by an insulator– metal-insulator- semiconductor FET ( MISFET ) Also called an IGFET (insulated gateFET) ost commonly called as OSFET etal xide Most commonly called as MOSFET (metal-oxide- semiconductor FET) FETs have high input impedance —since the control oltage is applied to a reverse biased junction or Schottky voltage is applied to a reverse biased junction or Schottky Barrier or across an insulator-----they are better suited (than BJTs) for controlled switching between conducting N) and non- onducting (OFF) states--- erefore better (ON) and non conducting (OFF) states therefore better for digital circuit implementation FETs are also more integrable Kaustav Banerjee Lecture 2, ECE 124A, VLSI Principles 4
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trange History Strange History…. .
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This note was uploaded on 12/04/2010 for the course ECE 134 taught by Professor York during the Fall '08 term at UCSB.

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Lecture2 - ECE ECE 124A VLSI Principles Lecture 2 Prof...

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