Summing Amplifier

Prelab and data table of measured voltages

constructed circuit

While the lab asked us to make a closed loop gain of around 2, we adjusted ours to be much smaller at 0.1912. We ran into problems with having the op amp getting saturated when using Vb outside of -2 to 2V. Most of the measured data points had a percent difference of less then 10 %. There were two points, Vb at -3V and 5V that gave differences of 12.6% and 10.6%. This makes sense that the greatest percent difference was for data points that had the biggest voltages used since they would be closer to saturation for the op amp.

Inverting Voltage Amplifier

Circuit diagram and
Vin/Vout table

Graph of Vin vs Vout

Constructed circuit

Based on the values we used for R1 and R2, our calculated gain was -0.470. We had to use a smaller ratio as we were having problems with our op amp reaching saturation with a higher closed loop gain. As can be seen in our graph, the slope of the line is close to the calculated gain with a percent difference of 5.68%. This was caused by the one outlier point we have in our data. 

Thevenin's Theorem

The Rth we calculated was 7.6k ohms. Our calculated Voc was nearly identical with what we measured in Analog Discovery.

Circuit for part 2(measuring voltage
between nodes A and B)

  

RL added to circuit
(RL was 7.5k ohms)

Actual measurement of open circuit voltage

Measured Voltage across RL

Dusk-to-Dawn Light

Prelab

Voltage of photocell in light(yellow)

Voltage of photocell in darkness(yellow)

Mesh Analysis 1, 2, & 3

Mesh Analysis 1

Since the same circuits were utilized from the previous nodal labs, we used the same readings and just worked out the prelab for each one.  For Mesh 1, there was a 1.13% difference for V1, and 1.31% for V2. This is minimal and even closed then what was achieved with the nodal lab.

Mesh Analysis 2

The voltage for V1 should of been 5 Volts as that resistor was in parallel with the 5V source.  We worked out 4.998V in our analysis.

Mesh Analysis 3

For this lab, we achieved a percent difference of 0.73% for V1. Using ohm's law, the calculated i1 using the measured V1 is -0.274 micro amps.  This gives a percent diff of 3.72%.

Nodal Analysis with Multiple Sources

              

Prelab

constructed circuit

Voltage reading of 10k ohm resister

The voltage across V1 was 5V as it was in parallel with the 5V PS. To get the current across the 10k ohm resistor, we used AD to measured the voltage of that resistor and used Ohm's Law getting a value of 0.3201 mA. In the prelab, we got that value as a negative which only means we chose the opposite direction for that current when conducting our analysis.

Nodal Analysis 3

constructed circuit

Prelab

actual resistances

Measured value of V1

This time when we did our prelab, we used the actual resistances used in our constructed circuit vice the given values in the manual which deviate only a little. The theoretical value we got in the prelab was 2.459 V and the actual value we measured was 2.466 which gives us a percent error of 0.30 %. The value we get for I1 ends up being -0.266 mA which just means we chose the opposite of the actual flow of current when doing our prelab.

Nodal Analysis

Prelab

             

Measured readings

V2

V1

The percent error for V2 was 1.38% and for V1 was 3.42%. This was partly attributed to our actual resistance values not exactly the same as our theoretical ones.

Practical Voltage and Current Measurement

Using voltage divider, the Vout should be 2.5 V using an ideal voltmeter. In reality, a voltmeter will never be able to have infinite resistance and so could affect your readings if dealing with resistances that are close to the internal resistance of your measuring device. In the pic on the left, we used 10M ohm resistors. Since the DMM's internal resistance is 10M ohm as well, it ends up being in parallel with the 10M ohm resistor it's measuring, lowering the equivalent resistance of the two to 5M ohm. This changes the circuit causing only 1.666 V to drop across the resistor we were measuring. In the right photo, we used much smaller resistors, only 100k ohm. Since they were so much smaller compared to the internal resistance of the DMM, it was able to act as an ideal voltmeter and not distort the readings as happened previously.

Solderless Breadboards, Open-circuits and Short-circuits

Purpose:

The goal of this lab is to give an introduction to equipment that will be utilized often for this class. The two main devices will be breadboards and digital multimeters(DMMs). For now, we will simply use the DMM to examine which connections are open and which ones are shorts on the breadboard. 

1. For the first configuration, we simply put two jumpers in the saw row on the same side. We measured 0.4 ohms. This what we expected to see as any nodes on the same row should be electrical connected thus making this a short circuit. 

2. For the next circuit, the jumpers were put in the same row, but this time with the channel between them. We see that this makes an open circuit as the meter is reading infinite resistance.

3. With the following circuit, again infinite resistance is measured. This is because not only are the jumpers on opposite sides of the channel, but they're in different rows as well. 

4. On the final circuit, the same setup is used from the previous one but this time a third jumper is put to connect the two separate nodes. As expected, the DMM now reads 0.7, minimal, ohms as this is a short circuit.