lec11 - 6.012 - Microelectronic Devices and Circuits - Fall...

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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 11-1 Lecture 11 - MOSFET (III) MOSFET Equivalent Circuit Models October 18, 2005 Contents : 1. Low-frequency small-signal equivalent circuit model 2. High-frequency small-signal equivalent circuit model Reading assignment: Howe and Sodini, Ch. 4, § 4.5-4.6
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 11-2 Key questions What is the topology of a small-signal equivalent cir- cuit model of the MOSFET? What are the key dependencies of the leading model elements in saturation?
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 11-3 1. Low-frequency small-signal equivalent cir- cuit model Regimes of operation of MOSFET: V GS V BS V DS I D V DS I D V GS V GS =V T V DSsat =V GS -V T 0 0 linear saturation cutoff Cut-off : I D =0 Linear : I D = W L μ n C ox ( V GS - V DS 2 - V T ) V Saturation : I D = I Dsat = W 2 L μ n C ox ( V GS - V T ) 2 [1+ λ ( V - V DSsat )] Effect of back bias: V T ( V BS )= V To + γ ( ± - 2 φ p - V - ± - 2 φ p )
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 11-4 Small-signal device modeling In many applications, interested in response of device to a small-signal applied on top of bias: V GS V BS V DS I D +i d v gs v bs v ds + - + + - - Key points: Small-signal is small response of non-linear components becomes linear Can separate response of MOSFET to bias and small signal. Since response is linear, superposition can be used effects of different small signals are independent from each other
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 11-5 V GS V BS V DS I D +i d v gs v bs v ds + - + + - - V GS V BS V DS I D i d v gs v bs
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This note was uploaded on 07/20/2009 for the course ELECTRICAL 6.012 taught by Professor Prof.jesúsdelalamo during the Fall '05 term at MIT.

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lec11 - 6.012 - Microelectronic Devices and Circuits - Fall...

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