Laboratory 8 - MOS Amplifiers

Please read and review the lab guidelines.

This lab does not require a report or prelab.

Objective:

This lab is intended to build understanding of SPICE simulation of MOS circuits and examine how they compare to real circuits.

Equipment and Components:

Procedure and Experiment:

Part 1 - Spice Simulations

  1. Using the values measured in lab 7, estimate the values of VSS to set the IDS equal to 1mA.
  2. Enter this circuit into PSPICE. Use the mbreakn model device for the NMOS transistor, and enter the values measured from last week's lab. In addition, use COX equal to 1.0pF/um2, W=5.0um, L=1.0um. Verify that the operating point is close to 1mA, and also verify that the model parameters are used correctly (examine the text output .lis file).
  3. Use SPICE to verify the operation. The output is at the drain node. What are the midband gain, the 3db rolloff points, and the input resistance as a function of frequency?
  4. Remove the bypass capacitor in SPICE, and short the drain to the supply. You now have a source follower circuit (similar to emitter follower). The output is at the source node. What are the midband gain, the 3db rolloff points, and the input resistance as a function of frequency?
  5. Repeat steps 1-4 for a drain current of 0.1mA. How does the ac response change?

Part 2 - Real Circuits

Repeat the spice simulations with real circuit elements. How close is actual operation compared to the spice predictions?