hw_7_sol - Homework 7 Solutions 7.12. An NFET is made with...

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Homework 7 Solutions 7.12. An NFET is made with t ox =4 nm, L =1 μ m, W =10 μ m, V T =1V, and μ lf = 500 cm 2 / V s . If the simple model is used, what should the width of the PFET be to get the same characteristics (apart from polarity). Let the low field mobility for holes be 200 cm 2 /V·s. From the long channel model (Equation (7.25)), () ' 2 ox Dsat GS T WC I VV L =− . Thus ' 2 ' 2 1 no xn GS T Dsatn n n Dsatp p p po xp GS T WC IW L L == = Thus W p = W n n p = 2 m 500 200 = 5 m Ans: 25micrometres. 7.13. An NFET and a PFET are made on the same chip, using the same process. The NFET has C ox ' =8.6 × 10 -7 F/cm 2 , t ox =4 nm, L =0.2 μ m, W= 15 μ m, V T =1.5 V, and lf =500 cm 2 /V·s. If the PFET is identical except for its mobility (200cm 2 /Vs) and width, W . a) What should W be for the PFET to make the characteristics the same as for the NFET, as predicted by the simple model? [] [] 2 15 500 NFET DS DNFET ox lfNFET GS T DS NFET NFET lfNFET WV I CV V L WX X ⎡⎤ ⎢⎥ ⎣⎦ × V where 2 DS GS T DS V X V is a constant that is the same for both the NFET and the PFET. We want this to equal that for the PFET: ( ) (200)( ) DPFET NPET lfPFET NPET I Setting these equal, we obtain: 15 500 = W PFET 200 W PFET = 37.5 m b) Find V DSsat and I Dsat for V GS - V T =1 V Using the simple model, 1 DSsat GS T V V = −=
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() ( ) 2 2 47 2 4 2 15 10 8.6 10 / 500 1 11 2 0.2 10 16 ox lf DSsat Dsat GS T DSsat WC V IV V V L cm cm F cm Vs cm mA μ −− ⎡⎤ =− ⎢⎥ ⎣⎦ ⎛⎞ ×× ⎜⎟ ⎝⎠ × = c) If velocity saturation is considered, How different are V DSsat and I Dsat for the NFET and the PFET compared to the simple model results? Express your result as a ratio (e.g., I DsatNFET / I DsatPFET and V DSsatNFET / V DSsatPFET ).
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This note was uploaded on 01/11/2012 for the course ECE 432 taught by Professor Lu during the Fall '08 term at Ohio State.

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hw_7_sol - Homework 7 Solutions 7.12. An NFET is made with...

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