ece340Fall03HW16sol - ECE 340 Homework XVI Fall 2003 Due:...

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ECE 340 Homework XVI Fall 2003 Due: Friday, November 21, 2003 (30 points total) 1. An n + -polysilicon-gate p-channel MOS transistor is made on an n-type Si substrate with N d = 5x10 16 /cm 3 . The SiO 2 thickness is 100Å in the gate region, and the effective interface charge Q i is 10 11 qC/cm 2 . Sketch the C-V curve for this device and give important numbers for the scale. Solutions: Looking at Fig. 6-16, the important numbers for the curve includes C i , V T , C min , and V FB , 14 72 8 3.9 8.85 10 3.4515 10 / 100 10 i CF c m d ε ×× == = × × 0.0259ln 0.389 d F i N V n φ The ms Φ can be obtained by looking up Fig 6-17, ms Φ = -0.2V. Or by assuming E F of n+ gate lies in the conduction band: 0.161 2 g ms F E V Φ= − + = (we take both answers, below we use ms Φ = -0.2V) 11 7 11 0 0.2 0.2466 3.4515 10 i FB ms i Q q VV C × =Φ − =− × 5 2 1.425 10 sF m a Wc m qN εφ × 1.14 10 / dd m Qq N W C c m × 7 7 1.14 10 2 0.2466 2 0.389 1.355 3.4515 10 d TF B F i Q V C × += × = × At maximum depletion, we have minimal capacitance: 82 7.328 10 / s d m c m W × min 6.045 10 / id CC c m × + The Figure is drawn similar to Fig 6-16 in the book. Because this is a pMOS, the channel will open if V
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ece340Fall03HW16sol - ECE 340 Homework XVI Fall 2003 Due:...

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