week_5_new - 30 Output resistance of current mirror V . DD...

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30 Output resistance of current mirror 2 D I , 2 GS V are unknowns and you have two equations, therefore you can find them both. (Then check for n t GS DS V V V - > ) Once you have 2 GS V b 2 1 GS GS V V = and 1 D I , that you will find is for the case your MOS#1 has infinite output resistance. If that is not the case then: . DD V 1 D I 2 D I 1 L W 2 L W R 2 2 2 ) ( 2 2 2 2 2 n t GS ox D D GS DD V V L W C I I R V V - = = - μ Assuming both transistors is in ideal MOS saturation 2 2 1 1 2 1 L W L W I I D D =
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1 2 1 1 1 2 2 (1 ) (1 ) DS D D GS V W L I I W L V λ + = + 1 2 2 GS GS DS V V V = = The goal is to increase out R so the current I D1 is independent of V DS1 . Source degenerate current mirrors To find 2 GS V , 2 D I : 2 2 2 2 2 ) ( ) ( 2 2 GS D S DD t GS ox n D V I R R V V V L W C I n = + - - = μ b again two unknowns, so you can find 2 GS V , 2 D I ( 2 2 GS DS V V = ) b check for n t GS DS V V V - > . R
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This note was uploaded on 02/19/2012 for the course ECE 455 taught by Professor Mohammadi during the Fall '10 term at Purdue University-West Lafayette.

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week_5_new - 30 Output resistance of current mirror V . DD...

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