1. Assignment

You are given a 0.4 μm N channel MOSFET with the characteristics given in Table 1. The

source resistance, RG = 50 

 and a load resistance of RL = 10 k

. The transistor has a

gate width of 10 μm. Find a bias circuit to give a voltage gain of 2.7 or greater using a 3

V power supply. You will need to determine the VGS, ID, and gm. Then verify your results

using SPICE and the full model as given in Table 1. Although values are given in the table

such as for Cox, these are calculated in SPICE. When NSUB and TOX are given (process

parameters), then SPICE will calculate KP, GAMMA, and PHI among other things. The

calculated values may be over ridden by entering the values into SPICE. In your work,

enter TOX and NSUB, but do not enter GAMMA, PHI. These have an “*” to indicate

you want SPICE to calculate these values. The values found by SPICE can be printed out

if you use the .OP command.

In the SPICE analysis, use the transient response where the sine wave has a frequency

of 10 kHz and the signal amplitude is 10 mV. Compare your predicted value for gain and

that found by SPICE. Then increase the input voltage to determine when “clipping” begins

to occur.

You are expected to work independently on this project. The GTA and I will be

happy to help you get over the rough spots.

2. MOSFET Parameters

A 0.4 μm gate length No-channel MOSFET has the following parameters derived from

data given in [1].

The equations used to generate the parameters in Table 1 are given below.

Cox =

ǫox

tox

(1.)

k′ = μnCox (2.)

Xd =

s

2ǫ



VDS − (VGS − Vt)



qNA

(3.)

Leff = Ldrwn − 2Ld (4.)

λ =

1

Leff

dXd

dVDS

(5.)

γ =

p2qǫSiNA

Cox

(6.)

φf = VT ln

NA

ni

(7.)

φ = 2φf (8