simple mppt schematic
Here's an example of MPPT of a small solar cell. Andy Pang sells some hobby style solar cells if you need some.. **broken link removed**
To understand MPPT, inspect how the Vout/Iout plots appear similar to bjt or mosfet - long saturation region followed by a dropoff to linear as the cell is loaded with heavier current. If you run a cell right at the edge of linear operation, that is MPPT.
Here is the example: I set up a small, panasonic 243318 under a lamp so it gave about 3v max with no load (Voc), and 1mA max output current short circuit (Isc).
Now sweep a load (50k pot) attached to the cell, and record Iout, Vout at several points. My graph appears similar to the normal saturation plot, but is pretty rough due to few points.. (sorry!) I estimated the linear region to be from about 2.92v to 0v, as my load sweeps from 300uA to 1mA.
I found MPPT at about 2v for this cell in this light. Take a look and let me know if you understand how to find it. The circuit to do so? Haha that is your puzzle! I say multiply Vcell * Iout, and sweep current from 0 to point of dropoff..