[SOLVED] differences between datasheet diagram and pspice output

[ehsantech]

Hello
Here is my circuit that I sweep current source from 1uA to 1ma

and I use spice model in Datasheet of 2N3904

as you see datasheet hfe-IC diagram and my pspice output (Ic/IB-Ic) they are so different in current 10mA (25C)



what is my mistake?

 

[esp1]

hi,
I use LTSpice, I would say that a Bf value, in your model, of 416 is very high, I see Bf typically around 200 to 250 in LTSpice.

As a test edit the Bf to say 200 and re-run you simulation, lets see what you get.
E

 

[ehsantech]

Thank you dear esp1
but my question is something different because I use datasheet spice model but the output are different.

 

[FvM]

Obviously the empirical B(Ic) characteristic is different from the used SPICE model.

It would be quite simple to find a 2N3904 datasheet from a different manufacturer with a curve that better fits the model prediction. But that's just the empirical evidence.

If you are seriously interested, it's time to study transistor models and their parameters. The models have paramters to describe a gain slope at lower currents, e.g. ISE (base emitter leakage saturation current). If it really matters, you can tune the parameters to match an empirical transistor characteristic.

 

[crutschow]

Note that the gain values shown in the data sheet graph are typical. The actual values can vary over a wide range (3:1 variation) so it just depends upon what value the spice model uses. The PSpice model may use a more conservative value rather than typical shown in the data sheet. For reliable design the worst-case minimum generally should be used.