lec9CctFamilies - Introduction to CMOS VLSI Design Circuit...

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Introduction to CMOS VLSI Design Circuit Families
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Circuit Families Slide 2 CMOS VLSI Design Outline Pseudo-nMOS Logic Dynamic Logic Pass Transistor Logic
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Circuit Families Slide 3 CMOS VLSI Design Introduction What makes a circuit fast? – I = C dV/dt -> t pd (C/I) V low capacitance high current small swing Logical effort is proportional to C/I pMOS are the enemy! High capacitance for a given current Can we take the pMOS capacitance off the input? Various circuit families try to do this… B A 1 1 4 4 Y
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Circuit Families Slide 4 CMOS VLSI Design Pseudo-nMOS In the old days, nMOS processes had no pMOS Instead, use pull-up transistor that is always ON In CMOS, use a pMOS that is always ON Ratio issue Make pMOS about ¼ effective strength of pulldown network V out V in 16/2 P/2 I ds load 0 0.3 0.6 0.9 1.2 1.5 1.8 0 0.3 0.6 0.9 1.2 1.5 1.8 P = 24 P = 4 P = 14 V in V out
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Circuit Families Slide 5 CMOS VLSI Design Pseudo-nMOS Gates Design for unit current on output to compare with unit inverter. pMOS fights nMOS Inverter NAND2 NOR2 A Y B A Y A B g u = g d = g avg = p u = p d = p avg = Y g u = g d = g avg = p u = p d = p avg = g u = g d = g avg = p u = p d = p avg = f inputs Y
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Circuit Families Slide 6 CMOS VLSI Design Pseudo-nMOS Gates Design for unit current on output to compare with unit inverter. pMOS fights nMOS Inverter NAND2 NOR2 4/3 2/3 A Y 8/3 8/3 2/3 B A Y A B 4/3 4/3 2/3 g u = g d = g avg = p u = p d = p avg = Y g u = g d = g avg = p u = p d = p avg = g u = g d = g avg = p u = p d = p avg = f inputs Y
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Circuit Families Slide 7 CMOS VLSI Design Pseudo-nMOS Gates Design for unit current on output to compare with unit inverter. pMOS fights nMOS Inverter NAND2 NOR2 4/3 2/3 A Y 8/3 8/3 2/3 B A Y A B 4/3 4/3 2/3 g u = 4/3 g d = 4/9 g avg = 8/9 p u = p d = p avg = Y g u = 8/3 g d = 8/9 g avg = 16/9 p u = p d = p avg = g u = 4/3 g d = 4/9 g avg = 8/9 p u = p d = p avg = f inputs Y
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Circuit Families Slide 8 CMOS VLSI Design Pseudo-nMOS Gates Design for unit current on output to compare with unit inverter. pMOS fights nMOS
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lec9CctFamilies - Introduction to CMOS VLSI Design Circuit...

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