EE331L Analog Electronics Laboratory 2

A MOSFET Operational Amplifier

Introduction:

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 result should provide capability comparable to that of the famous 741 opamp.

Procedures:

  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).

  Use current mirrors to bias your MOSFETs

  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.

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

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

  Waveforms

o   Simulated

o   Measured

  Frequency Response, slew rate, loading, etc.

  Power considerations

 

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