Been working on the two stage opamp for my Sundar. The first stage takes the current from the photodiode and turns it into a voltage with a certain amount of gain. The second stage applies a second gain as well as an offset via two digital (SPI) potentiometers.<\/p>\n
The first set of opamps I uses were 741s I had around. They did not work because the need +-9V and I am running on a 5V rail. The next set I picked up from Radio Shack were a bit better but still were not rail to rail. Next set I ordered from Digikey were rated rail to rail in the title, but only later did I find out that was only the case for larger voltages.<\/p>\n
Last set I am working on (again from digikey) was designed for low voltage but although the input is rated rail to rail, the output still is not.<\/p>\n
So after careful consideration and talking to every EE I know, I placed an order for some expensive opamps from Linear Technologies. These are rated for a single 5V supply with railt to rail inputs and outputs. Hope these work when they arrive early next week.<\/p>\n","protected":false},"excerpt":{"rendered":"
Been working on the two stage opamp for my Sundar. The first stage takes the current from the photodiode and turns it into a voltage with a certain amount of gain. The second stage applies a second gain as well … Continue reading