EE 330 Lect 29 Spring 2011

EE 330 Lect 29 Spring 2011 - EE 330 Lecture 29 Small-Signal...

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EE 330 Lecture 29 Small-Signal Models Comparison of MOS and BJT performance Basic amplifier architectures
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Quiz 20 Obtain the small signal model of the following circuit. Assume MOSFET is operating in the saturation region
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And the number is …. 6 3 1 2 4 5 7 8 9
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And the number is …. 6 3 1 2 4 5 7 8 9 7
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Quiz 20 Obtain the small signal model of the following circuit. Assume MOSFET is operating in the saturation region Solution: g m v gs v gs g 0 G D V I   0 m V g g I  0 11 EQ mm R ggg
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I D V DS V GS1 V GS6 V GS5 V GS4 V GS3 V GS2 Load Line Q-Point R 1 V IN (t) V OUT V DD V SS M 1 Graphical Analysis and Interpretation V GSQ =-V SS Device Model (family of curves)     2 1  OX DQ GS T DS μ C W I V -V V 2L Saturation region Linear signal swing region smaller than saturation region Modest nonlinear distortion provided saturation region operation maintained Symmetric swing about Q-point Signal swing can be maximized by judicious location of Q-point Review from Last Time
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V T V T0 V BS ~ -5V   BS T0 T V V V Typical Effects of Bulk on Threshold Voltage for n-channel Device 1 - 2 0.4V 0.6V Bulk-Diffusion Generally Reverse Biased (V BS < 0 or at least less than 0.3V) for n- channel Shift in threshold voltage with bulk voltage can be substantial Often V BS =0 Review from Last Time
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Small-Signal Model Extension     1 GS T DS D OX GS T DS GS DS GS T 2 OX GS T DS GS T DS GS T 0 V V V W I μC V V V V V V V V L2 W μC V V V V V V V V 2L T      BS T0 T V V V 0 0 0 Q Q Q V V GS G 13 V V DS G 12 V V G 11 V I y V I y V I y 0 0 0 Q Q Q V V B 33 V V DS B 32 V V B 31 V I y V I y V I y Q Q Q D D D 21 12 13 GS DS GS V V V V V V I I I y y y V V V m o mb g g g G I =0 B I =0 Review from Last Time
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Small Signal Model Summary OX m EBQ μC W gV L DQ o λI g BSQ m mb V g g 2 G S V gs V bs V ds i d i g i b B D Small Signal Network ds o bs mb gs m d b g v g v g v g i i i 0 0 Review from Last Time
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Relative Magnitude of Small Signal MOS Parameters OX m EBQ μC W gV L o DQ g λI 5E-7  2 mb m m BSQ g g .26g V    d m gs mb bs o ds i g v g v g v DQ OX m I L W C g DQ m EBQ 2I g V Consider: 3 alternate equivalent expressions for g m If μ C OX =100 μ A/V 2 , λ =.01V -1 , γ = 0.4V 0.5 , V EBQ =1V, W/L=1, V BSQ =0V   -4 2 2 OX DQ EBQ μC W 10 W I V 1V =5E-5 2L 2L  OX m EBQ μC W g V 1E-4 L 0 m mb g <<g ,g mb m g < g In this example This relationship is common In many circuits, V BS =0 as well Review from Last Time
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Large and Small Signal Model Summary ds o bs mb gs m d b g v g v g v g i i
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EE 330 Lect 29 Spring 2011 - EE 330 Lecture 29 Small-Signal...

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