HW 2

Due Friday 9/16 6pm

 
  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.