I am building my first project, a LED matrix. The matrix is controlled by a pic18F4550 and the rows are driven using a TLC5940 led driver (chose this chip for RGB later down the road). Right now I have a single line of LEDs working with each LED connected to ground. For a matrix would the best way to connect each column to ground be by using a shift register to drive transistors connected to each column?? If so what kind of transistor should I use and how do I tell that is the right transistor for future reference.