lec16 - 6.012 - Microelectronic Devices and Circuits - Fall...

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Unformatted text preview: 6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 16-1 Lecture 16 - The pn Junction Diode (II) Equivalent Circuit Model November 3, 2005 Contents : 1. I-V characteristics ( cont.) 2. Small-signal equivalent circuit model 3. Carrier charge storage: diffusion capacitance Reading assignment: Howe and Sodini, Ch. 6, §§ 6.4, 6.5, 6.9 Announcements: Quiz 2: 11/16, 7:30-9:30 PM, open book, must bring calculator; lectures #10-18. 6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 16-2 Key questions • How does a pn diode look like from a small-signal point of view? • What are the leading dependences of the small-signal elements? • In addition to the junction capacitance, are there any other capacitive effects in a pn diode? 6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 16-3 1. I-V characteristics (cont.) Diode current equation: I = I o (exp qV kT- 1) Physics of forward bias: n p F n F p • potential difference across SCR reduced by V ⇒ mi- nority carrier injection in QNR’s • minority carrier diffusion through QNR’s • minority carrier recombination at surface of QNR’s • large supply of carriers available for injection ⇒ I ∝ e qV/kT 6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 16-4 n p F n F p Physics of reverse bias: • potential difference across SCR increased by V ⇒ minority carrier extraction from QNR’s • minority carrier diffusion through QNR’s • minority carrier generation at surface of QNR’s • very small supply of carriers available for extraction ⇒ I saturates to small value 6.012 - Microelectronic Devices and Circuits - Fall 20056....
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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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lec16 - 6.012 - Microelectronic Devices and Circuits - Fall...

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