EE331L Analog Electronics Laboratory 2

A MOSFET Operational Amplifier


You have already become very familiar with opamp circuits. The BJT circuits you have studied so far suffer from a few shortcomings that can be improved in some instances by using MOSFETs. In this lab you will build your own discrete component operational amplifier using only MOSFETs. The end result should provide capability comparable to that of the all-to-famous 741 opamp.


  1. Build a Discrete Component Amplifier

  Design, simulate and implement a general purpose operational amplifier utilizing at least three stages, input differential, gain, and output.

  You may use your own design and may choose from any components present in the teaching lab, but all transistors must be MOSFETs (no BJTs or diodes).

  The input signal will be a sinusoid, 50 mVpp amplitude.

  You should be able to perform at least as well as 75% of the specs of the 741 opamp characteristics for: gain-bandwidth product, slew rate, low offset, and small output resistance.

  Use the function generator and oscilloscope to capture test waveforms from your amplifier before the competition.

  Do a Monte Carlo simulation in Multisim of your design to see how component variations will affect the performance of your amplifier.

  1. Test your circuit

  Once you have built your circuit to your satisfaction, we will test all of those circuits on the same platform.

  Anyone who can beat all of the 741 specs outright will win the prize this week (potentially everyone can win).

  If no one beats the 741, the circuit with the best overall performance wins the competition.

  You still need to meet at least the 75% mark to obtain full credit for the lab.


Analysis and Report:

Please complete a brief lab report (2-3 pages). Focus on explaining your design process. Explain how you chose the overall circuit design and the key components. Explain the important parameters and effects of your circuit, as well as how it could be improved in the future, or with more resources. Your report should address the following:

  Circuit Diagram


o   Simulated

o   Measured

  Frequency Response, slew rate, loading, etc.

  Power considerations


Your lab report is due at midnight on the Friday following the testing session.