EE 330 Lect 36 Fall 2011

EE 330 Lect 36 Fall 2011 - EE 330 Lecture 36 Cascode...

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EE 330 Lecture 36 Cascode Current Sources Cascaded Amplifier Design Special two-transistor configurations Differential Amplifiers Digital Circuit Design
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Current Sources/Mirrors Multiple-Output Bipolar Current Source and Sink Enk nk 0 E0 A I = I A    Q 0 Q n1 A E0 A En1 I n0 I 0 Q n2 I n1 Q nn I nn A En2 V DD Q p0 Q p1 Q p2 Q pn A Ep0 A Ep1 A Ep2 A Epn I p1 I p2 I pn A Enn Epk En1 pk 0 E0 Ep0 A A I = I AA Review from Last Lecture
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Current Sources/Mirrors Amplifiers both positive and negative currents npn current mirror amplifier E1 out in E0 A = A    ii Q 0 Q 1 A E0 A E1 i in I BS MI BS i out E1 E0 A M= A Review from Last Lecture
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Current Sources/Mirrors n-channel Current Mirror    0 1 out in 01 L W I = I WL M 0 M 1 W 0 ,L 0 I out I in W 1 ,L 1   2 OX 0 in GS0 T0 0 μC W I = V -V 2L   2 OX 1 out GS1 T1 1 μ C W I = V -V 2L If process parameters are matched, it follows that Current mirror gain can be accurately controlled Layout is important to get accurate gain (for both MOS and BJT) Review from Last Lecture
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Layout of Current Mirrors Example with M = 2 21 12 WL M=    Standard layout Better Layout 42 2 22 11 2W W L L M= W W L L          Even Better Layout 2 2W W L L W W L L         This is termed a common-centroid layout Review from Last Lecture
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Current Sources/Mirrors n-channel current mirror current amplifier 21 out in 12 WL =    ii M 1 M 2 W 1 ,L 1 i in I BS MI BS i out M= W 2 ,L 2 Amplifiers both positive and negative currents Review from Last Lecture
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Current Sources/Mirrors 0 k k0 0k L W I = I WL    M 0 M 1 W 0 ,L 0 I 1 I 0 M 2 I 2 M n I n W 1 ,L 1 W 2 ,L 2 W n ,L n V DD I 1 I 2 I n I 0 M 1 M 2 M n W 1 ,L 1 W n ,L n W 2 ,L 2 M 0 W 0 ,L 0 multiple output n-channel current sink array multiple output p-channel current source array Review from Last Lecture
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High-gain amplifier V IN V OUT Q 1 V DD V EE I B m V 0 -g A g V IN V OUT Q 1 V EE V CC V YY m1 V 01 -g A 2g Nonideal current source decreased the gain by a factor of 2 But the voltage gain is still quite large Can the gain be made even larger? Review from Last Lecture
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The Cascode Amplifier (consider npn BJT version) Q 1 Q 2 V XX V IN V SS V OUT I B V CC Actually a cascade of a CE stage followed by a CB stage but usually viewed as a “single-stage” structure Cascode structure is widely used Discuss Review from Last Lecture
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Cascode Configuration Comparisons V IN V OUT Q 1 V DD V EE I B m V 0 -g A g V IN V OUT Q 1 V EE V CC V YY Q 2 m1 m1 V 01 02 01 -g -g A g g 2g Q 1 Q 2 V XX V IN V SS V OUT I B V CC m1 V 01 g A β g    Q 1 Q 2 V XX V IN V SS V OUT V YY V CC Q 3 m1 m1 V 01 03 03 gg A g g +g  Can we design a better current source?
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EE 330 Lect 36 Fall 2011 - EE 330 Lecture 36 Cascode...

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