HW 2
Due Friday 9/16 6pm
- Grab
the SPICE Level 49 models for a 0.35um CMOS
process. You want the nominal,
fast, and slow models, which correspond to different (measured) performance of devices made in
the same process but on different wafers.
- Use HSPICE to estimate the value of
Vt, the quantity mnCox, and l for an NMOS transistor with a W/L of 35/0.35 with the nominal model.
To do this you will want to (for example) plot the square root fo Id vs. Vd for a diode connected
transistor (why?), or plot Id vs. Vgs for Vds=0.01V. You can use the AWAVES expression
builder to let you take square roots, derivatives, etc.
- Repeat this estimation for a
transistor with W/L = (50/0.5), (100/1), and (200/2) with the nominal parameters, and plot the
values of Vt, the quantity mnCox, and l vs. the channel
length.
- Repeat what you did in problem 2, but use the fast and slow models (just for
35/0.35 is fine, but do all of them if you want), and plot these points on the same plot as in
problem 3.
- Using the estimated parameters (of Vt, the quantity mnCox, and l ) for a 100/1
NMOS transistor with the nominal model, calculate by hand the value of Id, gm, ro, Vdsat assuming
Vgs=Vds=1V.
- Using your estimated parameters (of Vt, the quantity KP= mnCox, and l ) from the
previous problem, use HSPICE with a Level 2 model to plot Id vs. Vds for Vgs=1V and Vds ranging
from 0 to 5 volts. (I put a very simple level 2 model in the same web directory as the level
49 models above - you just need to change the parameters) On the plot, draw a horizontal
line with your calculation for Id, and a vertical line with your calculation for Vdsat. On
the SPICE text output, find the information about gm and ro at the operating point (ro isn't
given, but gds is - how do you convert?), circle it, and write your estimates for gm and ro along
with the percent error between your estimates and the spice-calculated values.
- Use the
SPICE Level 49 nominal model, and make the same plot as in the previous problem (put them both on
the same plot). Now create a new panel in awaves, and plot the output resistance for both
devices. You will need to use the derivative function in the expression builder in awaves to
do this.
- Vacuum tube
assignment (6 pages, 2.5 MB) Estimate gm, ro, and the maximum possible gain for the tube used
with a constant current source bias of 100mA on the plate and -75 V bias on the grid. In a
tube, the plate is sort of like the drain or collector of a transistor, and the grid is sort of
like the gate or base. You will have to estimate some derivatives from the graph for this
problem.
Some spice hints.
There's a file called hw2.sp in the web directory with the spice model files that may or may
not be useful to you. No guarantees.