Lab 5 - EE 420L
Buchaa2@unlv.nevada.edu
March 13, 2019
Again, this lab will utilize
the LM324 op-amp (LM324.pdf).
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
If we look at the circuit in DC we will see
that the capacitor causes the op-amp to have an open loop, and because of the
DC offset of the op-amp the integrator will cause the output to hit the rails. We
don’t see this in the hand calculations, but you can see it in the real circuit
and the simulation.
- Does the 100k have much of an effect
on the frequency response
The 100k resistor does not have any effect
on the frequency response. That is why we can neglect it as show above in the
hand calcs.
- 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.
- Is the phase shift between the input
and the output what you expect? Why or why not?
Simulation matches
hand calculations.
This is the
unity frequency calculated in the hand calculations. The amplitude of both
waves is approx. 1.3V and the phase shift is expected because we calculated the
phase shift to be 180 degrees difference.
- 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.)
Using the
values calculated in the hand calculations we can see that the values simulate correctly
and give expected results.
Something went
wrong with our circuit when we measured it.
The mean of our wave was correct, but as you can see it is defiantly not
a triangle wave. If you look at the wave you can see that it is within the 1V-4V
range, but when the input switches the output spikes to almost 5V as shown in
the Pk-Pk measurement. We tried many different capacitor
values with their corresponding resistor values and we got the same shape wave
every time. 
We did notice
a tradeoff between the capacitor and resistor values. The trade off is that the
larger the capacitor value the greater the error in the wave was. The smaller
the cap value the clearer the wave. That is why the value we picked was so
small(1.5n).
Conclusion: This
lab was assigned to help with the understanding of integrators and give us a
design problem to help show how integrators can be used as a tool.