E11 Lab #2
2007

Introduction to Op Amps

Information for your Lab Report

Lab report due the next time you come to lab.
This lab requires a formal lab report.

If you are having a lot of trouble with part of the report, please come see me.  I don't want the writing of the lab report to be an exercise in frustration, so if you get stuck, please don't hesitate to ask for help.  Also, if you find you are missing some data, or it just doesn't make sense, please talk to me before finishing your report.

1. The inverting configuration.

2. The non-inverting programmable-gain configuration.

The inverting configuration.

This lab requires a formal lab report.  However, make sure, that within that format, you include (at least) the following derivations/results for the inverting configuration.  They should be included as prose in your report (they are enumerated below only to make it easier to follow).

1. Show the derivation of the relationship between input and output for the inverting configuration.

   

2. Show your lab results (without distortion).

3. Do a MultiSim simulation of your circuit.

4. Compare your lab (measured) results directly to your expected (theoretical and MultiSim) results. 
   

5. Show your lab results (with distortion).  What is the limiting factor in the magnitude of the output of the op-amp?

Make sure all graphs and tables have appropriate labels and units.  Make sure every graph and table is referenced in the report.  Don't include large tables of numbers where a graph is more useful (if absolutely necessary, you can include such a table as an appendix).  Where possible, directly compare measured and theoretical results on a single graph/table.

The non-inverting programmable-gain configuration.

Make sure you include (at least) the following derivations/results for the non-inverting configuration.

1. Show the derivation of the relationship between input and output for the non-inverting configuration.

   

2. Consider the programmable non-inverting configuration shown below.

   

   1. Calculate the gains of the circuit  in terms of R_a, R_b and R_F for the four configurations of the switches:

   Sb	Sa	Gain
   open	open
   open	closed
   closed	open
   closed	closed

   2. Now calculate the gains when R_a=20kΩ, and R_b=10kΩ and R_F=20kΩ.

   Sb	Sa	Gain
   open	open
   open	closed
   closed	open
   closed	closed

   3. Present your lab results, and compare them to your expected results.  Calculate the error and speculate on its origins.  You should include experimental and theoretical results side-by-side (e.g., in the same table).
      
      

Include the following sections as an appendices:

• Appendix A. Verify the relationship between input and output for the non-inverting configuration of figure 1 and equation 1 of the article from EDN magazine. 

• Appendix B.Verify the relationship between input and output for the non-inverting configuration of figure 2 and equation 14 of the article from EDN magazine.

• Appendix C.For the circuit below, find values of R_a, R_b, R_c and R_d and R_F that give sixteen equally spaced gains (1, 2, 3, ... , 16) that are integer multiples of the lowest gain (in this case, 1) as the switches are opened and closed as shown.

  Sd Sc Sb Sa Gain open open open open 1 open open open closed 2 open open closed open 3 open open closed closed 4 open closed open open 5 open closed open closed 6 open closed closed open 7 open closed closed closed 8 closed open open open 9 closed open open closed 10 closed open closed open 11 closed open closed closed 12 closed closed open open 13 closed closed open closed 14 closed closed closed open 15 closed closed closed closed 16

  How could you expand this to N switches and 2^N gains?  (What is the relationship between the resistances?)

• Appendix D. (Extra, you needn't do this - 3 points) Consider the non-inverting configuration of figure 1 and equation 1 of the article from EDN magazine,   Show that, the circuit with N switches (as modified below), can not generate 2^N equally spaced gains that are integer multiples of the lowest gain.
  

• (Extra, you needn't do this - 3 points) For figure 2 and equation 14 of the article from EDN magazine show that, with N switches, it is not possible to generate 2^N equally spaced gains that are integer multiples of the lowest gain.

Make sure all graphs and tables have appropriate labels and units.  Make sure every graph and table is referenced in the report.  Don't include large tables of numbers where a graph is more useful (if absolutely necessary, you can include such a table as an appendix).  Where possible directly compare measured and theoretical results on a single graph/table.

Here is a link to the grading sheet I will use, so you can see how much each part of the lab is worth, and what I will be looking for.  Also refer to the formal lab report format.

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email me with any comments on how to improve the information on this page (either presentation or content), or to let me know if you had any particular difficulties with this lab.

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