Vgs when vds reaches vgs vta the channel vanishes at

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Unformatted text preview: es at y = L and the current holds steady at its saturation value. iD (vGS ,v DS ,v BS ) = 1 W * me Cox {vGS - VT (v BS )} 2 2a L vDS Clif Fonstad, 10/03 Lecture 12 - Slide 2 The gradual channel approximation - review cont. The full result is: Valid for v BS 0, and v DS 0 : iG (vGS ,v DS ,v BS ) = 0 and iB (vGS ,v DS ,v BS ) = 0 1 0 for [vGS - VT (v BS )] < 0 < v DS a 1 W 1 2 * iD (vGS ,v DS ,v BS ) = me Cox [vGS - VT (v BS )] for 0 < [vGS - VT (v BS )] < v DS 2a L a 1 W m C * v - V (v ) - a v DS v GS DS for 0 < v DS < [vGS - VT (v BS )] T BS L e ox 2 a with C* eox t ox ox The threshold voltage is written several different ways (all equivalent, of course) 1/ 2 1 VT (v BS ) VFB - 2f p-Si + g 2f p-Si - v BS with g * [2eSiqN A ] 1/ 2 Cox 1/ 2 1/ 2 1/ 2 = VFB - 2f p-Si + g 2f p-Si + g 2f p-Si - v BS - 2f p-Si [ [ = VT (0) + g {[ 2f p-Si - v BS ] {[ [ } 1/ 2 - 2f p-Si [ 1/ 2 } with VT (0) VFB - 2f p-Si + g 2f p-Si [ 1/ 2 The factor a is typically not included in the model because it is approximately 1 and contributes little to the accuracy or to our intuition and insight. Clif Fonstad, 10/03 Lecture 13 - Slide 3 MOSFET Characteristics (n-channel) Also: iG 0 iB 0 K = (W/...
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This note was uploaded on 07/20/2009 for the course CSAIL 6.012 taught by Professor Prof.cliftonfonstadjr. during the Fall '03 term at MIT.

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