Lab 4: Op Amp Success!

After much tribulation we decided to use a voltage divider and an op amp to supply 2.5V to the non-inverting input of our inverting op amp. A diagram of this 2.5V virtual ground can be seen in the following diagram below.


Virtual Grnd Op Amp

Since this is a single supply op amp (0-Vcc instead of +/-Vcc) the need for a virtual ground is paramount. As we realized just supplying 2.5V will not solve the problem of a functional op amp. Once we had the op amp virtual ground supplying 2.5V we connected it to another inverting op amp as shown in the circuit diagram below.


Inverting Op Amp with Virtual Grnd

Once we constructed this circuit, we then tested it with a multimeter to see what voltages were being output. We found that for a ~1V input from the Hall-Effect sensor's "push-push" configuration we obtained an output range of 0.73-3.5V or ~3V. The following diagram shows how we connected the Arduino, Hall-effect sensor, and Op amps together.



Op Amp Circuit

Finally, we compared the theorectical output voltage with the empirical data and found values to be close to expected using the following formula.



Inverting Op Amp Equation (V_Bias=2.5V)