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Unformatted text preview: Lecture 23, Slide 1 EECS40, Fall 2003 Prof. King Lecture #23 Warning for HW Assignments and Exams : • Make sure your writing is legible !! OUTLINE • MOSFET I D vs. V GS characteristic • Circuit models for the MOSFET – resistive switch model – small-signal model Reference Reading • Rabaey et al.: Chapter 3.3.2 • Howe & Sodini: Chapter 4.5 Lecture 23, Slide 2 EECS40, Fall 2003 Prof. King MOSFET I D vs. V GS Characteristic Long-channel MOSFET V DS = 2.5 V > V DSAT Short-channel MOSFET V DS = 2.5 V > V DSAT • Typically, V DS is fixed when I D is plotted as a function of V GS Lecture 23, Slide 3 EECS40, Fall 2003 Prof. King MOSFET V T Measurement • V T can be determined by plotting I D vs. V GS , using a low value of V DS : DS DS T GS n D V V V V L W k I − − ′ = 2 I D (A) V GS (V) V T Lecture 23, Slide 4 EECS40, Fall 2003 Prof. King Subthreshold Conduction (Leakage Current) • The transition from the ON state to the OFF state is gradual. This can be seen more clearly when I D is plotted on a logarithmic scale: • In the subthreshold ( V GS < V T ) region, This is essentially the channel- source pn junction current.source pn junction current....
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- Fall '08
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