switching PNP transistor from forward active to saturation states

[yefj]

Hello, i have a PNP 2N5087 component which is connected as shown bellow.
for forward active PNP we need the Emitter-base forward biased and base-collector reversed biased.
(emitter)P-N(base) needs to be V_E>V_B to forward biased.
(base)N-P(collector) reversed biased V_base>V_collector.
The base is a voltage divider between V1 and VDD.
given the datasheet bellow Vbe=0.85 .
but its wrong it should be Veb=0.85 for active region.
i know that the difference between active and saturation is the Vce voltage drop.

how do i put in saturated region my PNP transistor?
should i change my circuit to be able to change the bias from forward active to saturared?
Thanks.
https://pdf1.alldatasheet.com/datasheet-pdf/view/11478/ONSEMI/2N5087.html

 

[yefj]

Hello FVM, i have achןeved my goal. i just got to the conclution that the data sheet plot is not accurate, and i am trying to recreate the plot 9

--- Updated Apr 11, 2023 ---

UPDATE:
using VCE i know that whn its small then its saturated.
but the saturation current is very small.
also Ic/Ib is about 2.
How do i increase the Ic current?
How do i increase the HFE?
Thanks.

--- Updated Apr 11, 2023 ---

UPDATE 2:

Hello , As you can see bellow i got a better result is saturation region with much higher IC current.
Hfe=3
I need some physical intution which would get me the same 45mA Ic creent with HFE=10?
Is there some theoretical explanation which could help me?
Thanks.

 

[danadakk]

Your sim begs the following questions and observations :

1) Your 90 and 100 ohm Rs in the base circuit just crazy low values.
Normally one would see biasing with 10's - 100's of K ohm R's.

2) You Ic is limited by the two 100 ohm R's in the C-E path and the 5V supply,
basically 5V / 200 ohms = ~ 25 mA

3) What actually are you trying to accomplish ? Just to make this sim match
the graph of Vbesat and Vcesat in the datasheet ? Or is this a real design with
design goals as a switch ?


Regards, Dana.

 

[yefj]

Hello Dana , exactly.I am trying just to recreate the plot in the data sheet.
"Just to make this sim matchthe graph of Vbesat and Vcesat in the datasheet ?"

I have got the resistor valuev by a math i did taking plot data from data sheet.
What could you reccomend (physics wise) to increase HFE in saturation from 3 to 10?
Thanks.

 

[danadakk]

The graph in the datasheet is termed "characterization data" for part and is usually a average
of many parts tested. So re-creating the graph not really possible with a sim as you have no
characterization data.

But producing a specific graph for specific conditions doable.

However then you have the issue how accurate is the spice model, many are over simplified
and not capable of exact reproduction of conditions.

And then you have the various attempts at modeling bipolar transistors :

https://www.chu.berkeley.edu/wp-content/uploads/2020/01/Chenming-Hu_ch8-2.pdf

Should it be a wave equation physics model predicting electron probability of states, momentum,
at any point in time ? Or a incredible simple model so simple its not of much use (no nonlinearities,
no reactive BW limiting elements)......:

Regards, Dana.