DC operating points of npn

[prcken]

Hi,
I got the DC operating points as below, I am confused about what's the implication of the vbci (intrinsic b-c voltage) for circuit design. and how do i know the build-in voltage and the transition voltage from saturation region to the linear region from the DC operating points print.
Thanks!

 

[dick_freebird]

Are you sure that the "i" is not "internal" (the voltage at
the junction's depletion region, not the terminal voltages
which include Ic*Rc and Ib*Rb drops? That interpretation
makes the vbci useful for gauging saturation.

 

[prcken]

Are you sure that the "i" is not "internal" (the voltage at
the junction's depletion region, not the terminal voltages
which include Ic*Rc and Ib*Rb drops? That interpretation
makes the vbci useful for gauging saturation.

I am not sure, just googled and found there is a website says it's intrinsic, but I can understand it has the meaning of internal.
why we check vbc? i think for npn in linear region, we just need to check vbe > 0.7 V or so (built-in voltage) and vce > 0.2 V or so(what is called for npn?)

 

[dick_freebird]

What matters to saturation is the forward current in the
B-C junction and the minority carrier population it supports.
Vbc is the best proxy for that, that you are given by the
usual models. Ic does not distinguish Ice (majority carrier)
vs Icb (minority carrier) usefully. Vbe-Vce incorporates the
I*R drops and again you do not know the partitioning.

The 0.7V number is very rough, does not follow temperature
or doping. You might need to bench characterization to get
a better "map" though.

 

[D.A.(Tony)Stewart]

The word Intrinsic resistance of the PN junction will apply here as it is a critical internal metric of the bulk region that interfaces with the conductors.

Diode Inc (nee Zetex) seems to have invented the metric Rce , which is the effective collector emitter resistance above saturation.

You can measure Rs or Rce or Rbe or ESR of any diode or transistor including LED's by picking the asymptote at rated saturation current and finding the zero crossing voltage.

Silicon small signal parts are just under 0.6V threshold and often rated at 0.7V with nominal at 0.65 just like yours....

Plot the VI curve and find the Rce. Then compare with Diodes Inc. parts.

BTW they have ultra-low Vce_sat so they rate transistors with 50:1 for IC:Ib instead of 10:1 like most.

 

[prcken]

...Vbe-Vce incorporates the
I*R drops and again you do not know the partitioning...

I found the definition here


So, for npn in linear region, vbci need to be < than some value. if Vbe_on = 0.7, and Vce_sat = 0.2, Vce need to be larger than 0.2, then vbci < 0.5 is the condition to check the npn in linear region, right?

- - - Updated - - -

You can measure Rs or Rce or Rbe or ESR of any diode or transistor including LED's by picking the asymptote at rated saturation current and finding the zero crossing voltage.

Silicon small signal parts are just under 0.6V threshold and often rated at 0.7V with nominal at 0.65 just like yours....

Plot the VI curve and find the Rce. Then compare with Diodes Inc. parts.

BTW they have ultra-low Vce_sat so they rate transistors with 50:1 for IC:Ib instead of 10:1 like most.

Thank you!
Yes, I can simulate the zero crossing voltage (Early Voltage, VA). I am simulating the spectre, VA can also be printed out. on the schematic, it shows vbci along with ib and ic, so i think vbci is an important parameter need to be checked in design. the beta (ic/ib) can be as high as several hundreds in this process I am using.

 

[D.A.(Tony)Stewart]

the beta (ic/ib) can be as high as several hundreds in this process I am using.

Saturated beta tends to be only 10% of linear beta, but there is more to Diodes Inc patents (Zetex) in doping.

Beware never assume hFe of Beta is used for switch mode or Vce(sat)

Look for Ultra low Vce(sat) or Rce (sat)