Note that sf is the 'squared factor' which is usually 2 - but does vary with transistor and I have accounted for this in my calculations. I could use the quadratic equation... Approximating the value by setting this value to 2, but this doesn't do me any good because there is no 'a' - not that I can readily identify anyway. I would also prefer to not assume a squared factor of 2.

Any help pointing me in the right direction would be helpful.