Op-Amps II

This was another lab assignment dealing with operational amplifiers. We replaced the network of the previous lab assignment by a seperate voltage source. We also explored the idea of replacing the input and feedback resistors. Here is the circuit diagram for this lab assignment.

Given a nominal fixed resistor R1=10kohm, we were told to determine Rf in order to achieve a gain of -10. To achieve such a result we simply multiplied R1 by 10 to get 100Kohm. The negative sign takes care of itself through the inverting amplifier. Then we obtained actual resistors and measured values of for R1 and Rf, respectively which are listed in the table below. Next, we were asked to compute Iop given that Vsen=1V. Here were the results that we obtained:

Next we were instructed to build the circuit as pictured in Figure 1 in the photo up above. 

We set the power supply to 0.25 V and used a common node on the breadboard for the circuit ground. We were asked to complete three sets of data for three different desired input voltages. For each desired input voltage, we were asked to measure the actual input voltage, output voltage, as well as the voltage across the feedback resistor. And from these, we were to calculate the current Iop coming out of the op-amp using the formula Iop=Vop/1 kohm. 

Next, we were told to de-energize the sensor and the op-amp power supplies. Then we were told to insert an ammeter in series with with the 15-V power supply so that the ICC could be measured. We then re-energized the op-amp power source and the sensor supply and set Vsen= 1V and we measured a value of 0.107 mA for ICC. We then de-energized both supplies once more and moved the ammeter in order to measure the current going into the op-amp from the -15 V power supply, which is the IEE. We then measured the value of IEE and it's value came out to be -1.010 mA. We then confirmed KCL for our op-amount at that operating point, Iop=.107-1.010=-.903mA. Next, we were require to find the power at each of the 12 V power supplies, which is shown below.

We were now told to de-energize both power supplies and add a 1kohm resistor across the Vout terminal:

Given that Vsen=1V, we computed or measured another set of measurements for Vin, Vout, Vrf, Iop, Icc, and Iee:

Now we were required to show that KCL holds for these op-amp conditions in the below. We were then required to determine to power supplied by each of the 15 V power supplies at this operating point, which is also shown in the photo below:

For our extra credit opportunity, we to determine the value of Rf to achieve a gain of -5. Here is what we obtained:

And finally, we were asked to create a corresponding table like we had created earlier: