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Modeling >> Semiconductor Devices >> Pspice Modeling of BJT curve Ib vs Vbe
https://designers-guide.org/forum/YaBB.pl?num=1123271781

Message started by vjoshi on Aug 5^th, 2005, 12:56pm

Title: Pspice Modeling of BJT curve Ib vs Vbe
Post by vjoshi on Aug 5^th, 2005, 12:56pm

Now I have setup my circuit as follows. There is a current source at the base with step curent of 200mA and then a resistor of 1 G ohm is connected . So how do i measure for getting Ib vs Vbe curve . I am getting a linear curve having a slope of 1 when i run the probe for Ib vs V: Q1(b) (ie ) voltage across Base and emitter.
Since the Base emitter junction is acting like a diode it should give me a flat curve for voltage less than threshold voltage and then at the voltage when the diode turns on it should give a vertical straight line high current at that threshold voltage.
So can u advice where i am doing wrong or can u refer to someone who could help me out.

Title: Re: Pspice Modeling of BJT curve Ib vs Vbe
Post by Geoffrey_Coram on Aug 18^th, 2005, 9:59am

A step current of 200mA? Could be that's too large, and the junction current is linearized to avoid blowing up the exponential.