Op Amp Lab

In this lab, a 741 op-amp was used to create inverting amplifier circuit under the pretense of creating a signal conditioning circuit for a sensor.

A voltage divider was devised to get a voltage of one volt for the V_IN and mimic a sensor's output.
The following data was collected on the components we used.

 Above is the layout of our circuits.

I_V1 = 8.95 mA
I_V2 = 0.95 mA
Because these aren't equal to each other, we couldn't go on to the last page of the lab because he lab was written in anticipation of each group getting a 3rd voltage source, but only 2 were available for each.

Equivalents HW using PSpice

Here's some screenshots for the evidence.

On the last one, after selecting the trace cursor to display, I used the Trace>Cursor>Peak to get teh peak wattage.

Thevenin and Norton Equivalents in PSpice

We modeled circuits in PSpice and used DC sweeps to o determine their Thevenin and Norton equivalents.

In order to do this in the first circuit, we placed a current source I2 across the terminals that we were interested in and then used a DC Sweep to change it's value from 0A to 1.0A. After running the simulation, a trace of "V(I2:-)" was added to plot the voltage across the current source I2.

 The y-intercept gave the Vth and the slope of the line gave the Rth because V=I*Rth.
Thus, the Vth = 20V and Rth = 6 Ohms.

Then we worked out the Norton equivalent. We did this by replacing the current source I2 with a Voltage source that was varied from 0 volts to 1.0V by increments of 0.1V.

Here the y-intercept gave us the I_N = 3.335 A and the slope gave G_N = 0.17 S.
In the last problem, I found the load that maximizes the power dissipation.
I put a resistor across the terminals that had values of { RL } and I set RL's value with a Global Parameter. This global parameter was swept from 100Ohms to 5kOhms with 100Ohm increments. I ran the simulation and got the following graphs. The top one was arrived at through a linear sweep, and the bottom through a octave sweep. The peaks show at 250microW with RL = 1kOhm, as expected.

Thevenin Equivalents' Equity

The purpose of this lab was to find a Thevenin equivalent of a circuit and model it to see how accurate it was.

The V_Th = 8.65V,
the R_Th = 66.0Ω,
and the I_Th = 131mA.

Here's a picture of our circuit.

Here's a the table of the components we used.

 Here's a table of the results we got from those components followed by another table of components we used.

 

However, the components in the seoncd table didn't really get the time needed to be used. We had started the lab too late and had to leave. Instead of making the whole class come back on Friday to finish the last page of the lab, Professor Mason allowed us to call it quits.

PSpice Fun

After installing PSpice, I had to run Capture Student as administrator to get the PSpice menu to show up in it.
I had to import some libraries to get the parts I need to use, and then it was simply place parts in a sensible pattern and connecting them with wire.

Below is my PSpice for working out the last problem of the 8th WebAssign assignment.

More pictures from Node Analysis

This shows a reading for our V₁ during the last problem when we were trying to make it and V₂ equal to 9V.

Nodal Analysis is for Knowing Nerd Noggins

We (James Dunn and I) used nodal analysis to determine the theoretical voltage between two points and a reference node AKA "ground" and the currents coming from two voltage sources.

Circuit Diagram

I'll get a better picture from James soon.

Our theorectical values for V₂ and V₃ were 10.26V and 8.67V respectively.
We determined that I_{Bat 1} and I_{Bat 2} were 17.4mA and 1.48mA, which would give power supplies of 208.8mW and 13.35mW respectively.



In the last part, for extra fun, we figured out what voltages we would need to load across the circuit to make both V₂ and V₃ equal 9V. We worked out that V_L1 would be 9.9V and V_L2 would be 10.98V. To get these particular load voltages, we would need to use a voltage divider to bring 12V down to these voltages.

We did this with a resistor box of 213Ω in series with V_bat1 and 103Ω in series with V_bat2. We got as close as 9.09V for V₂ and 8.99V for V₃, after fiddling with the resistances a bit. :) Our currents became 9.90mA and 8.61mA for I_bat1 and I_bat2 respectively.