The electric behavior of a reverse-biased PN junction diode is modeled by measuring the value of voltage V present across the diode and the value of the corresponding current I running through this diode, the voltage V varying within a range of values including the value of diode breakdown voltage. A representation of a function ln ⁡ ( I - I s ) according to voltage V is established from the measured values of current I and of voltage V, IS being the saturation current of the diode. A linear function representative of a substantially linear portion of the function, characterized by voltages V greater than breakdown voltage VBK in terms of absolute value, is determined. An avalanche multiplication factor MM is then calculated by MM = 1 + ⅇ ( - slbv · V + bv bv ) , with parameter slbv equal to the ordinate at the origin of the linear function, and parameter slbv/bv equal to the slope of the linear function.