Problem 1 only. Chart included for reference. a Clara Univers Department of Elec
ID: 2083994 • Letter: P
Question
Problem 1 only. Chart included for reference.
a Clara Univers Department of Electrical Engineering No Name: Write Name and Page Number on each page Include this page with homework Write on One Side of 8% x 11 paper Do not Staple Due: 5-30-2017 ELEN 153 Problem Set #6 Grades will be pro-rated for late submission. Fall 2017 1. Construct the zero-bias Capacitance model for an nFET using the Capacitance Model in the handout. Calculate for all three Operating Regions. Lateral diffusion length- 0.14 um Source Drain) length minus Lateral diffusion length 2.9 Hm, sion capacitance per unit area 4x Zero bias side-wall junction (diffusion) capacitance per unit perimeter 7x10 -10 F/m. 2. Consider the NOT gate shown in Fig. 7.11 (see back side) when an external load of CL 76 fF is conne to the output. Note that the electrical channel length is LE0.8 um. a Find the input capacitance of circuit. b) Find the values of Rn and Rp. c) Calculate the rise and fall times for the inverter.Explanation / Answer
Solution:
Zero bias capacitance model for nFET is as follows:
given, tox = 30 nm
L = 0.8 um
W = 3.4 um
Ld = Lateral diffusion length = 0.14 um
LD = LS = 2.9 + 0.14 = 3.04 um
Cj0 = 4 x 10-4 F/m2
Cj0 sidewall = 7 x 10-10 F/m
Calculations:
1. Oxide capacitance per unit area:
Cox = eox / tox
= ( 3.9 x 8.85 x 10-12 F/m ) / 30 x 10-3 um
= 3.5 x 10 -2 fF/um / 30 x 10-3 um
= 1.17 fF/um2
2.Total gate capacitance:
Cg = WLC ox
= 3.4 um x 0.8 um x 1.17 fF/um2
= 3.18 fF
3. Overlap capacitance:
CGSO = CGDO = W x Ld x Cox
= 3.4 um x 0.14 um x 1.17 fF/um2
= 0.55 fF
4. Cgb under zero bias :
Cgb = Cox W Leff = Cg - (2 x CGSO) .... 2 times because gate-source and gate- drain overlap
Cgb = 3.18 fF - ( 2x 0.55 fF ) = 2.08 fF
5. Diffusion capacitance:
CD = Cj0 x W x LD = 4 x 10-4 F/m2 x 3.4 um x 3.04 um
= 0.4 fF/um2 x 3.4 um x 3.04 um
= 4.13 fF
6. Sidewall capacitance:
Cs = Cjsw0 x (2LD +W )
= ( 7x 10-10 F/m )x (2 x 3.04 um + 3.4 um)
= ( 7x 10-16 F/um )x (2 x 3.04 um + 3.4 um)
= 6.60 fF
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