Lab 5 - EE 420L
Authored
by Hongzhong Li,
Today's
date : 03/05/2015
Email:lih12@unlv.nevada.edu
Lab
description - Op-amps III, the op-amp integrator
- Calculate the frequency response of the following circuit. Ensure you show your clear hand calculations.
- What can you neglect to simplify the calculation?
We can neglect
R2 because R2 (100k) >> R1 (1k) therefore R2 || R1 approximately equal to R1. - Does the circuit work if you remove the 100k? Why or why not?
The circuit will not work if we removed the 100k resistor.
This is because the big resistor is needed in the circuit to discharge
the big capacitor so that the circuit will not suddenly jump to a very
high output and become saturated.
- Does the 100k have much of an effect on the frequency response?
The 100k resistor does not have much of an effect on the
frequency response,its only purpose is to stablize the circuit and
thats why it has to be big so that R2 || R1 = R1 assuming R2>>R1.- Verify your calculations with experimental results.
- Show, at the unity-gain frequency of the integrator, that the input and the output have the same peak values.
 |  |
| Unity- Gain frequency - Input = output | R2 removed does not affect the circuit's output |
- Is the phase shift between the input and the output what you expect? Why or why not?
 | The
phase shift is close to 90 degree (negative reading due to measuring
from input to output instead of output to input. Therefore the phase
shift is what I expected as the output is correctly "integrating"
(Increase in voltage as input goes up) |
- 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.)
If
we use a bigger resistor then we can get a smoother triangle output
graph as it gives more time for the capacitor to charge and discharge.
By increasing our input we can see that we will need to use a bigger
resistor or a smaller capacitor to achive the same result. For
example, if the input signal is centered at 2.5 and the positive swing
is .2 Volts and the negative swing is also .2 Volts, the capacitor in
the feedback will charge and discharge at the same rate causing the
output to be porportional square wave.
Back up work
This concludes the lab, the completed lab is send to my email as back up.
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