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Published byGretchen Caldwell Modified over 2 years ago

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Transistor nMOS Q channel = CV C = C g = ox WL/t ox = C ox WL V = V gc – V t = (V gs – V ds /2) – V t v = E (mobility) E = V ds /L Time for carrier to cross channel: t = L / v C ox = ox / t ox

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nMOS Linear I-V Now we know –How much charge Q channel is in the channel –How much time t each carrier takes to cross

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nMOS Operation CutoffLinearSaturated V gs < V t V gs > V t V ds < V gs –V t V gs > V t V ds > V gs –V t I ds 0 I ds = ( V gs –V t –V ds /2 ) V ds I ds = ( V gs –V t ) 2

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Esempio 180 nm process W/L= 4/2 nm nm t ox =40Å cm 2 /(V·s) V t = 0.4V = C ox W/L = 180 * (3.9*8.85 *10 -14 F/cm)/(40*10 -8 ) =155 V 1)I dsmax @ (V gs =1V) = 155 V V) 2)I ds (V gs =2V, V ds =1V) = 155 V

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I-V Characteristics

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CMOS Inverter n-well n-well contact (n+) p+ diffusions polysilicon n+ diffusions substrate contact (p+) polysilicon contacts diffusion contacts

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DC Transfer Curve For a given V in : –Plot I dsn, I dsp vs. V out –V out must be where |currents| are equal in Transcribe points onto V in vs. V out plot

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Operating Regions RegionnMOSpMOS ACutoffLinear BSaturationLinear CSaturation DLinearSaturation ELinearCutoff

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Beta Ratio If p / n 1, switching point will move from V DD /2

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Inverter a Carico Resistivo V out I

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Inverter a Carico Attivo V out I

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