EE 330 Lect 35 Fall 2011

EE 330 Lect 35 Fall 2011 - EE 330 Lecture 35 Current Source...

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EE 330 Lecture 35 Current Source Biasing Current Sources and Mirrors Differential Amplifiers
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Differential amplifier Q 1 V in1 -V EE R C1 Q 2 R C1 V DD I EE V OUT1 A E1 =A E2 V in2 V OUT2   11 1 1 2 2 Cm OUT IN IN Rg     V V V   2 1 2 2 OUT IN IN V V V Very useful circuit This is a basic Op Amp Review from Last Lecture
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Model of Current Source V 1 I 1 Current Source LARGE SIGNAL S R XX I V 1 i 1 Current Source SMALL SIGNAL IN R “Reasonable Current Source” I XX independent of V 1 and R S large Small-signal model of current source want R IN large Ideal Current Source V 1 I 1 Current Source LARGE SIGNAL I V 1 i 1 Current Source SMALL SIGNAL I XX independent of V 1 IN R= Review from Last Lecture
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Current Sources/Mirrors Q 0 V CC R Q 1 A E0 A E1 Load I 1 I 0 Q 0 V CC R Q 1 A E0 A E1 I 1 I 0 V 1 I 1 Current Source Review from Last Lecture
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Current Sources/Mirrors Q 0 V CC R Q 1 A E0 A E1 Load I 1 I 0   CC 0 V -0.6V I R If the base currents are neglected
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Current Sources/Mirrors Q 0 V CC R Q 1 A E0 A E1 Load I 1 I 0   CC 0 V -0.6V I R If the base currents are neglected BE0 t V V 0 S E0 I =J A e BE1 t V V 1 S E1 I =J A e since V BE1 =V BE2 1 E1 0 E0 A II A    Behaves as a current source ! Actually termed a “sink” current since coming out of load Note I 1 is not a function of V 1 (defined on previous slide) So is ideal with this model !! 06 CC E1 E0 V . V A AR Review from Last Lecture
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Current Sources/Mirrors Q 0 V CC R Q 1 A E0 A E1 I 1 I 0 I 1 Multiple Outputs Possible Can be built at sourcing or sinking currents Also useful as a current amplifier MOS counterparts work very well and are not plagued by base current Current Sink Review from Last Lecture
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Current Sources/Mirrors Q 0 Q 1 A E1 I 1 I 0 Q 2 I 2 Q n I n A E2 A En A E0 Multiple-Output Bipolar Current Sink Ek k0 E0 A I = I A   
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Current Sources/Mirrors Multiple-Output Bipolar Current Source Ek k0 E0 A I = I A    V DD Q 0 Q 1 Q 2 Q n A E0 A E1 A E2 A En I 1 I 2 I n I 0
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Current Sources/Mirrors Multiple-Output Bipolar Current Source and Sink nk I =? 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 pk I =?
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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
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Current Sources/Mirrors Q 0 Q 1 A E1 I out I in A E0 Termed a “current mirror” Output current linearly dependent on I in Serves as a current amplifier Widely used circuit npn Current Mirror E1 out in E0 A I = I A   
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Current Sources/Mirrors npn current mirror amplifier out =?
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This document was uploaded on 01/31/2012.

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EE 330 Lect 35 Fall 2011 - EE 330 Lecture 35 Current Source...

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