MIT6_012S09_lec09

# MIT6_012S09_lec09 - Lecture 9 MOSFET(II MOSFET I-V...

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Unformatted text preview: Lecture 9 MOSFET(II) MOSFET I-V CHARACTERISTICS(contd.) Outline 1. The saturation region 2. Backgate characteristics Reading Assignment: Howe and Sodini, Chapter 4, Section 4.4 6.012 Spring 2009 Lecture 9 1 1. The Saturation Region Geometry of problem Regions of operation: • Cut-off: V GS < V T – No inversion layer anywhere underneath the gate I = D • Linear: V GS >V T and 0 < V DS < V GS -V T : – Inversion layer everywhere under the gate W V DS = I D L • μ n C ox V GS − 2 − V T • V DS 6.012 Spring 2009 Lecture 9 2 The Saturation Region (contd.) • Saturation: V GS > V T , and V DS > V GS - V T : – Inversion layer “pinched-off” at drain end of channel I D = W • μ n C ox [ V GS − V T ] 2 2 L Output characteristics: • Last lecture : To derive the above equations for I D , we used for Q N (y), the charge-control relation at location y: Q ( y ) = − C [ V − V ( y ) − V ] N ox GS T for V GS – V(y) ≥ V T . . Note that we assumed that (a) V BS = ⇒ V GS = V GB , and (b) V T is independent of y. See discussion on body effect in Section 4.4 of text. 6.012 Spring 2009 Lecture 9 3 The Saturation Region (contd..) Review of Q N , E y , and V in linear regime as V DS increases: Ohmic drop along channel de-biases inversion layer ⇒ current saturation ....
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## This note was uploaded on 11/07/2011 for the course COMPUTERSC 6.012 taught by Professor Charlesg.sodini during the Spring '09 term at MIT.

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MIT6_012S09_lec09 - Lecture 9 MOSFET(II MOSFET I-V...

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