Curve fitting of three curves to single equation


#1

I have extracted data from image and do some curve fitting. I tried manually Engauge Digitizer software to extract numeric data from image Files three curve’s data .csv files. Now I can have three curve fitting from each csv file. Each curve are temperature dependent

Vce25 = a25Ic + b25log(Ic) + c25 —(1) @ temperature Tvj=25C
Vce125 = a125Ic + b125log(Ic) + c125 —(2) @ temperature Tvj=125C
Vce150 = a150Ic + b150log(Ic) + c150 —(3) @ temperature Tvj=150C

Vce,Tc,Tvj are variables & a,b,c are constants how to find them?

I want to combine these three curves, coefficients can be made temperature-dependent to a single equation { Vce = f(Ic,Tvj) }. How to do thisi in R?


#2

All these three curves is basically just one curve: Vce = Tvj( alc + blog(lc) +c) Where Tvj = 25, 125 or 150. More information is needed to solve this equation.


#3

In the image you can see three curves, each curve is dependent on temperature. The equation in the question are my assumption for best fit for individual curves, but i need to estimate Vce at any given Ic and Tvj(eg: at Ic=200, Tvj=50C Vce=?).