# Cannot find “reverse saturation current” of base-emitter junction in the data-sheet

Regarding the reverse saturation current $I_{ES}$ aka $I_{EO}$ of an NPN transistor, according to Ebers–Moll Model:

$I_E = I_{ES} (e^{V_{BE}/V_T} -1) -\alpha_RI_{CS}(e^{V_{BC}/V_T}-1)$

Approximated form becomes:

$I_E \approx I_{ES} (e^{V_{BE}/V_T} -1)$ or even more simply:

$I_E \approx I_{ES} (e^{V_{BE}/V_T})$

Let's say in a design somehow I want to quantify $V_{BE}$ drop more accurately for a desired 1mA emitter current, rather than just taking $V_{BE}$ as 700mV.

And in that case knowing the above formula and $I_{E}$ = 1mA, $V_{T}$ = 26mV I want to quantify $V_{BE}$ as:

$V_{BE} \approx 26×10^{-3}×ln(10^{-3}/I_{ES})$

So above to quantify $V_{BE}$, I'm missing the value for the parameter $I_{ES}$.

Here is the datasheet for 2N2222 transistor.

Isn't this parameter called reverse saturation current between the base-emitter junction? Either I cannot find this parameter in the data-sheet, or it is just not there. Is there another name for $I_{ES}$ or it is not presented?

You might be able to extract it by curve fitting Figure 4, which shows the typical relationship between $V_{BE}$ and $I_C$.
Even easier, you can find a SPICE model for 2n2222, which will likely include a reasonable value of $I_{ES}$ determined by a similar curve-fitting technique.