Hi All, Just posing a little question on the design of photodiode amplifiers. It is interesting how, so often, when you look into doing something you haven't done before, you run into interesting bits of 'common knowledge' that you don't know, and have a hard time finding!
In this case, I am designing a simple color sensor. I originally was going to cook book it with a pre-made sensor IC that I2C communicated, but ran into two months of programming difficulties, non-documented features and bugs, and have finally decided to 'simplify' things, and just roll my own.
Now, National has Sensor Webench, that will basically let you take a sensor, and they will build the amplifiers you need for you. Interesting, but you don't LEARN anything. Also, if you need a sensor not on their 'list,' you are pretty muich SOL. I need a visible light photodiode, and I didn't find one that I liked on their list.
So, I decided to try rolling my own, and looking at both their examples, and in AoE, I see one interesting thing - a negative bias on the photodiode. So, my first question - how is this negative bias usually generated? And at what voltage? It is just 'assumed' that you know these things already! I am trying to build a very portable device, and wanted to use a single 3.3V supply for everything.
Thanks for any advice and good sources for more research.
Charlie