This week has been mostly research and testing designs/circuits. I did a lot of research into how opamps are used in circuits and studied datasheets for a few different opamps, including the INA217, which I think will be the one I end up using. The biggest breakthrough I had in researching this week is beginning to understand the power staging necessary for this type of circuit. Most opamps require a positive voltage as well as a negative voltage and ground to operate. My understanding at the beginning of this project was that the negative voltage and ground were the same thing, but my research this week is showing otherwise. I found a few designs that give both positive and negative voltages, as well as a 0v ground that I will be building this week. I would like to be able to incorporate 48v phantom power into my design if possible, so I have been looking for ways to have both 48vdc and 15vdc (required input for most opamps). This part I have not figured out yet.

This week I will plan to build in stages. In a conversation with my boss at work, we determined that the four main stages that I will need built are the power stage, a balanced input stage, the amplification stage, and a balanced output stage. Building these separately and combining should work. I am placing an order for components this afternoon so that I can hopefully have them in hand late this week or early next.

The other main thing that I did this week is building and testing some circuits that I found online to see how opamps function in a circuit. While I was not able to find any that worked for my application as I thought they would, I did learn quite a bit about the functionality of opamps, including how gain control works. Below is a picture of a few of the circuits that I tried (there were more. Some were not nearby for the picture and more still were taken apart for the components).

Test circuits
A few of the circuits that I built and tried