Lab 5 - EE 420L Engineering Electronics II 

Author: Matthew Meza

Email: mezam11@unlv.nevada.edu

February 27, 2015 

Op-Amps III: The Integrator!

• Watch the video op_amps_III, review op_amps_III.pdf (associated notes), and simulate the circuits inop_amps_III.zip.
• Read the write-up seen below before coming to lab.
  

• Learn and experience how to use an integrator to transform a square wave input into a triangle wave output!
  

For the following questions and experiments assume VCC+ = +5V and VCC- = 0V.

• Calculate the frequency response of the following circuit. Ensure you show your clear hand calculations.
• What can you neglect to simplify the calculation?
• Does the circuit work if you remove the 100k? Why or why not?
• Does the 100k have much of an effect on the frequency response?  

Simulation Circuit	Ft = 157 Hz

Part 2:

• Show, at the unity-gain frequency of the integrator, that the input and the output have the same peak values.
• Is the phase shift between the input and the output what you expect? Why or why not?

Sinusoidal Signal, Ft = 159 Hz	Square Wave Signal, Ft = 159  Hz

Conclusion:

The calculated unity-gain frequency is Ft = 159 Hz. In the sinusoide above, we can see that the peak values are approximately

equal. However, in the square wave signal above, we see that the output (triangle wave) has a peak value greater than the input.

The two peak values for the square wave signal are nonetheless the same order of magnitude. In addition, we expect to see a

phase shift of about 90 degrees based off of our calculations. In both of of the images above we can an approximate 90 degree
phase shift.

Part 3:

• Next, design, simulate, and build a square-wave to triangle wave generation circuit. 
• Assume the input/output frequency is 10 kHz and the output ramp must swing from 1 to 4 V centered around 2.5 V.
• Show all calculations and discuss the trade-offs (capacitor and resistor values, input peak, min, and average, etc.)

Input and Output

Experimental (Notice the voltage scales are different)

Conclusion:

The output is not exactly as we expected but this can be due to many factors. For example, the output cannot get as

close to the rails as we would like, which is simply a flaw in the op amp. In addition, the 2.5 Vm voltage must be very

close to the 2.5 Vin voltage so that we do not have an excessive DC offset. By increasing the resistor, we are able to

theoretically increase the swing of the output which.

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