3 - BJT vs CMOS: Active mode Collector Condition #1:...

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1 ECSE334 – Introduction to Microelectronics ECSE 334 Introduction to Microelectronics Roni Khazaka Lecture #3 ECSE334 – Introduction to Microelectronics 2 Khazaka - 2008 BJT vs CMOS: Active mode npn Collector Base Emitter i B i C i E BE v + BC v + CE v + Condition #1 : Forward bias EBJ BCon BC v v < V v BEon 7 . 0 Condition #2 : Reverse bias CBJ BEon BE v v > V v BCon 4 . 0 OR V v CE 3 . 0 > ECSE334 – Introduction to Microelectronics 3 Khazaka - 2008 BJT vs CMOS: Active mode D G S D i G i GS v + GD v + DS v + Condition #1 : Induce a channel V V V t 7 . 0 5 . 0 = t GS V v > OV t GS v V v + = Condition #2 : Pinch-off at drain OV DS v v > OR t GD V v < V v OV 3 . 0 2 . 0 = ECSE334 – Introduction to Microelectronics 4 Khazaka - 2008 I-V Characteristics in Active Region BJT CMOS + = A CE V v S C V v e I i T BE 1 β C B i i = + = A DS OV ox n V v v L W C 1 2 1 2 μ () + = A DS t GS ox n D V v V v L W C i 1 2 1 2 0 = G i ECSE334 – Introduction to Microelectronics 5 Khazaka - 2008 I-V Characteristics in Active Region Exponential versus square law relationship: Greater variability of i C . Note that v OV is typically kept at 0.2V to 0.3V. Device dimensions: Emitter area in BJT can be used to scale Is (Range 1 to 10). The W/L ratio is the equivalent parameter in CMOS (range 0.1 to 100): device scaling much more useful design parameter in CMOS. In CMOS V A depends on device geometry while for BJT transistors it is only a process parameter. ECSE334 – Introduction to Microelectronics 6 Khazaka - 2008 Low Frequency Small Signal Π Model C B E r π g m v π v π + - r o D G S g m v gs v gs + - r o BJT CMOS
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2 ECSE334 – Introduction to Microelectronics 7 Khazaka - 2008 Low Frequency Small Signal T Model D G S 1/g m i s r o BJT CMOS i s C B E r e i e r o α i e ECSE334 – Introduction to Microelectronics 8 Khazaka - 2008 Low Frequency Small Signal Model
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This note was uploaded on 01/27/2011 for the course ECSE 334 taught by Professor Anashamoui during the Spring '10 term at McGill.

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3 - BJT vs CMOS: Active mode Collector Condition #1:...

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