EE 330 Lect 15 Fall 2011

EE 330 Lect 15 Fall 2011 - EE 330 Lecture 15 Devices in...

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EE 330 Lecture 15 Devices in Semiconductor Processes the MOS Transistor
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n-Channel MOSFET L EFF L W Source Drain Gate Bulk Review from Last Time
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n-Channel MOSFET Operation and Model V BS V GS V DS Apply small V GS (V DS and V BS assumed to be small) I D =0 I G =0 I B =0 Depletion region electrically induced in channel I D I G I B Termed “cutoff” region of operation Review from Last Time
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n-Channel MOSFET Operation and Model V BS V GS V DS Increase V GS more I D R CH =V DS I G =0 I B =0 Inversion layer in channel thickens I D I G I B (V DS and V BS small) R CH will decrease Termed “ohmic” or “triode” region of operation Review from Last Time
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n-Channel MOSFET Operation and Model V BS V GS V DS Increase V DS I D =? I G =0 I B =0 Inversion layer thins near drain I D I G I B (V BS small) I D no longer linearly dependent upon V DS Still termed “ohmic” or “triode” region of operation Review from Last Time
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Triode Region of Operation V DS V BS = 0 V GS I D I G I B ( ) OX T GS CH C V V 1 W L R µ = 0 I I V 2 V V V L W μC I B G DS DS T GS OX D = = = For V DS larger Review from Last Time
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n-Channel MOSFET Operation and Model V BS V GS V DS Increase V DS even more (beyond V GS -V T ) I D =? I G =0 I B =0 Nothing much changes !! I D I G I B (V BS small) Termed “saturation”region of operation Review from Last Time
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Saturation Region of Operation V DS V BS = 0 V GS I D I G I B ( ) 0 I I V V 2L W μC I B G 2 T GS OX D = = = For V DS in Saturation Review from Last Time
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Model Summary V DS V BS = 0 V GS I D I G I B ( ) GS T DS D OX GS T DS GS DS GS T 2 OX GS T GS T DS GS T GB 0 VV V W I μ C V V V V L2 W μ C V V V 2L I =I =0 T  = −− <   ≥− Note: This is the third model we have introduced for the MOSFET Cutoff Triode Saturation ( ) OX T GS CH C V V 1 W L R µ = ( Deep triode special case of triode where V DS is small ) Review from Last Time
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Model Summary V DS V BS = 0 V GS I D I G I B ( ) < = T GS DS T GS 2 T GS OX T GS DS GS DS DS T GS OX T GS D V V V V V V V 2L W μC V V V V V V 2 V V V L W μC V V 0 I T Observations about this model: ( ) ( ) ( ) D 1 GS DS G 2 GS DS B 3 GS DS I V ,V I V ,V I V ,V f f f = = = This is a nonlinear model characterized by the functions f 1 , f 2 , and f 3 where we have assumed that the port voltages V GS and V DS are the independent variables and the drain currents are the dependent variables GB I =I =0 Review from Last Time
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Graphical Representation of MOS Model ( ) GS T DS D OX GS T DS GS DS GS T 2 OX GS T GS T DS GS T 0 VV V W I μ C V V V V L2 W μ C V V V 2L T  = −− <   ≥− GB I =I =0 Review from Last Time 0 0.5 1 1.5 2 2.5 3 0 1 2 3 4 5 VDS Cutoff Triode Saturation I D V DS 2 D OX DS W I = μC V L V GS1 V GS2 V GS3 V GS4 Deep Triode RegionRegion
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Model Extensions 0 50 100 150 200 250 300 0 1 2 3 4 5 1 A V λ = V DS I D Projections intersect –V DS
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This document was uploaded on 01/31/2012.

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EE 330 Lect 15 Fall 2011 - EE 330 Lecture 15 Devices in...

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