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Unformatted text preview: 6.012  Electronic Devices and Circuits Lecture 25  CMOS Scaling Rules  Outline Announcements Handouts  Lecture Outline and Summary; on web: CMOS scaling Course evaluation  at the end of lecture today (approx. 11:45) Final  Monday, Dec. 15, 9:00 am  noon, duPont Gymnasium Review  Intrinsic high frequency limits for transistors: w T Shortcircuit current gain: best can do from CE or CS Unity gain frequency: BJT: w T 2D e /w B 2 = 2 m 2 (used Einstein rel.) e V th /w B MOSFET: w T 3 m e (V GS  V T )/2L 2 (this needs discussion) Revisiting the quasistatic assumption (^ same form; ain't it neat!!) CMOS gate delay and power Review of Lecture 16 results: Gate Delay = 12 n L min / m n (V DD V T ) 2 2 V DD P @max. f C L V DD 2 /GD = K n V DD (V DD V T ) 2 /4 ave Power density issue: have to add this as well CMOS scaling rules The issues and challenges Approaches: Dimension scaling Scaling voltages as well Summary of rules Clif Fonstad, 12/03 Lecture 25  Slide 1 BJT shortcircuit current gain, b j w ) sc ( b F w b : w b = g p /(C p +C m ) w t : w t @ g m /(C p +C m ) Zero, w z : w z = g m /C m Note: w z > w t >> w b (= w t / b F ) log w log b  b F w b w t w z Low frequency value: 3dB point, Unity gain point, sc w g m = g m = 1 t [ C p + C m ] { g m t trB + C eb , dp + C cb , dp } { t trB + kT C eb , dp + C cb , dp ] [ qI C } In the limit of large I C : w t ( BJT ) 1 2 D eB = 2 m e V thermal = 2 2 t trB w B w B Clif Fonstad, 12/03 Lecture 25  Slide 2 MOSFET shortcircuit current gain, b j w ) sc ( w t : w t @ g m gs +C gd ) Zero, w z : w z = g m /C gd Note: w z > w t log w log b  w t w z Unity gain point, /(C sc W * L 1 w ( MOSFET ) g m g m = m e C ox [ V GS V T ] = 3 m e [ V GS V T ] t 3 [ C gs + C gd ] C gs 2 WLC * 2 L 2 t trCh ox Clif Fonstad, 12/03 Lecture 25  Slide 3 Looking more at w T for BJTs and MOSFETs: For a MOSFET we have  V T ] w ( MOSFET ) 3 m e [ V GS t L 2 2 [ V GS V T ] The average Efield in the channel, E...
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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.
 Fall '03
 Prof.CliftonFonstadJr.

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