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Ve311 Homework #4

Note:

(1) Please use A4 size papers.

(2) Please use the SPICE model on page 3 for simulation and calculation.

1. [MOSFET DC Biasing, 60%] Use the drain current equations below.

Donβt consider channel-length modulation and body effect. Assuming

Wdrawn / Ldrawn = 20 Β΅m / 2 Β΅m, sketch IX of M1 as a function of VX

increasing from 0 V to VDD = 5 V. (Note: finish this part before the

midterm exam)

ππ = Β΅π§

ππ¨π±

π

ππππ

[(πππ β πππ)πππ β

π

π

πππ

π

] (NMOS in triode region)

ππ =

π

π

Β΅π§

ππ¨π±

π

ππππ

(πππ β πππ)

π

(NMOS in saturation region)

ππ = Β΅π©

ππ¨π±

π

ππππ

[(πππ β |πππ|)πππ β

π

π

πππ

π

] (PMOS in triode region)

ππ =

π

π

Β΅π©

ππ¨π±

π

ππππ

(πππ β |πππ|)

π

(PMOS in saturation region)

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2. [MOSFET Small-Signal Model] Assume Wdrawn / Ldrawn = 20 Β΅m / 2 Β΅m.

(a) [20%] Use Pspice to plot the drain current of a NMOS as a function

of VDS increasing from 0 V to 5 V, at VGS = 1 V, 1.5 V and 2 V. Label

the off, triode and saturation regions for each curve. Derive ro from each

curve in the saturation region and compare it with hand-calculation result.

(b) [20%] Use Pspice to plot the drain current of a NMOS as a function

of VGS increasing from 0 V to 3 V, at VDS = 5 V. Derive gm from the

curve when VGS = 2 V and compare it with hand-calculation result.

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Vacuum permittivity (ππ¨) = π. ππ Γ ππβππ (F / m)

Silicon oxide dielectric constant (ππ«

) = π. π