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Jacob Carpenter (Jymmy Navarates)

Introduction
The purpose of this lab was to gain a better understanding of how an op amp is set up and changes an input voltage.

Methods
This lab was broken down into three parts: Calculation, Simulation, and Measuring. The first part was calculating the
expected outputs from various input voltages with different op-amp voltages. The second part involved creating the same
circut in LTSpice and comparing it’s output voltages with those that we calculated. The third part involved creating the
circut using an analog discovery module and measuring the output voltage.
In Part One of the lab, we used our knowledge of inverting op amp setups to calculate that with our setup we were
getting a gain of -10.007
In Part Two, we had the same gain, however the falloff as our op amp approached it’s maximum output happened
sooner than expected (below the input 6V).
In Part Three, our gain was slightly lower than calculated and the falloff was even sooner than in the calculation and
simulation.
Figure 1 - Op amp set up

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Results
Table 1 summarizes the results for all output values, our Resistors were 992 and 9990 kΩ respectively.

Table 1 – Nominal and measured resistor values

Input Voltage Calculated output Simulated output Measured output Simulated output Measured output
(mV) for 6V voltage for 6V voltage for 12V voltage for 12V voltage

100 -1.007 -1.007 -1.010 -1.007 -1.012

200 -2.014 -2.014 -2.025 -2.014 -2.022

300 -3.021 -3.021 -2.702 -3.021 -3.034

400 -4.028 -4.028 -3.985 -4.028 -4.045

500 -5.035 -4.738 -4.517 -5.038 -5.053

600 -6.042 -4.855 -4.614 -6.046 -6.064

700 -7.049 -4.968 -4.612 -7.054 -7.074

Figue 2 shows our oscilloscope output in blue and input in orange.

Conclusions
In Part One, we found that once the gain was calculated, we could very quickly calculate what we expected the
outcome to be.
The output voltages trailed below what we thought they would around the limit of the supplied voltage, this isn’t how
we treat an ideal op amp in reality.
The simulation results matched our theoretical calculations closely up to a point, but diverged as the input voltage
approached the limits of the op amp's power supply, highlighting the practical limitations of real op amps compared to
ideal models.
The measured output voltages consistently showed earlier clipping than both calculated and simulated outputs, which
may be attributed to internal losses or tolerances in the actual op amp or imperfections in the Analog Discovery setup.

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This lab reinforced the concept that while theoretical calculations provide a baseline, real-world components have
limitations that must be considered during circuit design.
The discrepancies between measured and simulated values at higher input voltages suggest that power rail limitations
and loading effects play a more significant role in real circuits than in simulations.
The gain values calculated and simulated were nearly identical, confirming that our resistor values and understanding
of the inverting op amp formula were correct.
To get our measured output voltage, we had to divide the height of the wave by two, as peak to peak is the only type
of output the ADM can measure.
Our circuit's performance under a ±6V supply was notably constrained compared to a ±12V supply, demonstrating
how increasing supply voltage can extend an op amp's linear output range.
Variations in the measured output could also be due to resistor tolerances, temperature effects, or limitations in our
measurement equipment, but the consistency between simulated and measured results makes this unlikely.
The lab showed how simulations are a helpful middle ground between theoretical design and practical testing, often
capturing real-world behavior more accurately than pure calculations.
Understanding where and why real circuits diverge from ideal predictions is crucial for designing reliable and efficient
analog systems, it would be interesting to see if there is a repeatable pattern to it, so it can be accounted for in calculations.
The early voltage falloff in the physical circuit highlighted the importance of understanding the voltage swing
limitations of the specific op amp model used.