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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 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

3 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

4 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 * F/cm)/(40*10 -8 ) =155  V  1)I (V gs =1V) = 155  V   V)   2)I ds (V gs =2V, V ds =1V) = 155  V  

5 I-V Characteristics

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

7 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

8 Operating Regions RegionnMOSpMOS ACutoffLinear BSaturationLinear CSaturation DLinearSaturation ELinearCutoff

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

10 Inverter a Carico Resistivo V out I

11 Inverter a Carico Attivo V out I


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