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Cascading Op-Amp Lab

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In this lab we used a dual input/output op-amp to design a circuit that would sum and invert two input voltages and then perform a second sum and inversion to yield a final result. As seen below, the first op-amp would yield the inverse of the sum of half of V1 and half of V2. With inputs of 1 and 2 volts this would yield -1.5V. The second op amp uses a voltage divider for the non-inverting input to ensure the circuit is below saturation voltage. The output of the first op-amp is connected to the inverting input of the second op-amp to invert the voltage from the first stage and yield a positive output voltage from the second op-amp. As seen above, the output voltage was different from our anticipated voltage but the sign of the voltage was as expected. The output of the first stage was much closer to the anticipated value from the calculations. When we plugged in the output from the first stage into the calculation with the actual resistances of the resistors used ...
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Inverting Voltage Amplifier Lab

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In this lab, we designed an inverting op-amp and tested the output voltages and various input voltages to test the operation. Below is our design for an inverting op-amp with a gain of 2. Vin (Volts) Vout (Volts) -3 3.58 -2.5 3.58 -2 3.58 -1.5 3.16 -1 2.11 -0.5 1.06 0 0 0.5 -1.02 1 -2.07 1.5 -3.12 2 -4.17 2.5 -4.25 3 -4.23 3.5 -4.24 4 -4.24 The table shows the output voltages measured at various input voltages. As seen above, the saturation voltages were 3.58V and -4.24V. The circuit response was linear from -1.5 to 2 volts, essentially between saturation voltages. The average gain for the op-amp was -1.743. The op-amp inverted the input voltage and our gain was nearly 2 for our circuit. The most interesting observation was that the positive and negative saturation voltages were not equal in magnitude.
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Lab 6: From Dusk Till Dawn

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Lab 6: From Dusk Till Dawn In this lab we created a simple circuit using a breadboard, resistors, a transistor, a photocell, and an LED. A power supply is connected to the circuit. When the light levels are low, the photocell has a very high resistance and at high light levels it has a low resistance. The BJT acts as a switch in this circuit. When it is dark, the photocell has a high resistance which causes current to flow through the LED causing it to light up. When it is bright in the room, the photocell has a low resistance and the BJT sends no current through the LED.  For the pre-lab we calculated the voltage, V B across the photocell with a resistance of 5k ohm and 20k ohm, respectively.  We operated the circuit and measured voltage across the photocell. Measured voltage with the photocell covered was 3.2 V versus 3.33 V predicted. Measured voltage with the photocell uncovered was 1.1 V versus 1.7 V predicted.
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Lab 5: Mesh Analysis

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Lab 5: Mesh Analysis Joel Cook March 13, 2018 Purpose: The purpose of this lab is to analyze different circuits using mesh analysis to solve for unknown quantities before building and measuring the quantities to compare against predicted values. Mesh Analysis I: We analyzed the circuit in the diagram and predicted that the voltage drop across the 6.8k ohm resistor would be 4.2V and across the 20k ohm resistor would be 2.38V. I performed the mesh analysis by inspection, which means finding the current in each loop by summing the resistors in the loop, subtracting the resistors shared with other loops and accounting for the power supplies. The matrices generated can be solved by hand using reduced row echelon form or using a calculator's matrix functions.  The measured voltages were 2.36V and 4.36V, respectively. The predicted voltage was within 4% of the measured voltage. Mesh Analysis II: For the second circuit diagram, we used mesh analysis an...
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Lab 4: Nodal Analysis III

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Lab 4: Nodal Analysis III March 8, 2018 Purpose: In this lab, we use nodal analysis to analyze a circuit with multiple sources to predict currents and voltages. Next we construct the circuit and take measurements to confirm our predictions. We analyzed the following circuit: By nodal analysis, we find the voltage, Vc, as the only unknown. We calculated the voltage to be 2.408V, as shown below: The lab asked for voltage V1 which is Vc-0 or 2.408V. We were also asked for current, I1, which we calculated to b2 0.272 mA. Next we constructed the circuit and measure V1 and I1 directly. As shown, we measured the voltage to be 2.45V, a difference of 1.7% from predicted, and 0.35mA, a difference of 22%. Conclusion: The lab was very successful in predicting the voltage drop across a resistor by nodal analysis. Although the difference between actual and expected current was more than 20%, it was still an acceptable means of predicting cur...
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Lab 3: Nodal Analysis

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Lab 3: Nodal Analysis March 6, 2018 Purpose: In this lab we use nodal analysis techniques for circuits with multiple power supplies. By analyzing the currents at circuit nodes, we can calculate what the voltage at those nodes will be. For the pre-lab we analyze circuit on paper before building the circuit, taking measurements and comparing results. Below is the pre-lab analysis that was conducted on the circuit shown: The voltages predicted were 2.36V for V1 and 4.36V for V2. Next we constructed the circuit as shown below: We used the Analog Discovery tool to provide the required power supplies and took measurements with a DMM. We measured the voltages as 2.34V at V1 and 4.33V at V2. This is a difference of 0.8% for V1 and and 0.7% for V2.  Conclusion: The results for the measured and expected voltages are very close and better than I anticipated. The lab was successful and shows that nodal analysis is an accurate means of analyzing a ci...
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Lab 2: Practical Voltage and Current Measurement

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Practical Voltage and Current Measurement Joel Cook March 1, 2018 Purpose:  The purpose of this lab is to construct a circuit and take measurements to explore the behavior of non-ideal voltage measurements. Taking measurements of a circuit affects the circuits operation and this help will help determine to what extent. Data: Pre-lab: We began by calculating the measured voltage, V out, of the circuit with an ideal voltmeter that contributes no resistance to the circuit. As shown, the voltage measured would be 2.5V. We calculated the equivalent resistance with the attached DMM in terms of Rm, the internal resistance of the meter. Data: We constructed the circuit as shown in the photo below. The resistors used are 10Mohm resistors. We measured the voltage with the following tool and laptop: We read 0.335 Volts as shown below. We estimated the internal resistance of the analog device as shown: We calculat...
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