Hello,I want to test the delay of a pulse when NPN is saturated and non saturated state.
I know it depends on the level of the pulse.
From the datasheet and abothe manual i have tried to recreate the state oj the junctions.
At first EB junction must be forward. I have tried to build the circuit below.
As you can see the BE junction is active,also you can see the Vce is very high.
Base current and collector current are attached.
How do i know if my NPN is saturated or active acording to the datasheet attached?
LTspice file is attached.
Datasheet for 2N2369 Motorola Transistors | Octopart
View and download the latest Motorola 2N2369 Transistors PDF Datasheet including technical specifications

https://www.ece.mcgill.ca/~grober4/...PICE/chapter4/Chapter 4 BJTs web version.html

 

The device is saturated when the Vce is ≤Vbe.

Here's the sim showing saturated and unsaturated switching behavior by using two different base resistor values:

 

Hello There is no such plot in the datasheet shown belo for linear state,there are no plots at all.
waht datasheet you use and what is the number of the plot for linear state?
Thanks.

https://octopart.com/datasheet/2n2369-motorola-40844554

 

waht datasheet you use and what is the number of the plot for linear state?

I didn't use the data sheet.

The non-saturated plot is when the collector voltage doesn't go to near zero when on (yellow trace).

 

If you put a Schottky diode from Base to Collector, it will keep you out of saturation. When the C gets 0.4V below B the diode steels the excess base current and holds the transistor just out of saturation. The transistor will be much faster.

The turn off delay time is very much related to how hard you over drive the transistor, how long the transistor has been in saturation, and how you turn off the base.

I have worked on speeding up power transistor for 40+ years and have built machines that measure "storage delay". There are testers on the market that I designed part of that measure dynamic and static values like this. There are testers that are no longer on the market that do this also, but we no longer make them ( PNP and NPN ).

I normally do not work with small transistor like that but the principal is the same. Ask questions.

 

f you put a Schottky diode from Base to Collector, it will keep you out of saturation. When the C gets 0.4V below B the diode steels the excess base current and holds the transistor just out of saturation. The transistor will be much faster.

That helps a lot with general purpose transistors that have a long storage delay, not so much with high-speed switching transistors, such as the 2N2369.

 

That helps a lot with general purpose transistors that have a long storage delay, not so much with high-speed switching transistors, such as the 2N2369.

For years I have used the highest voltage power transistor I can get. The HV silicon is slow. A 1000V or 1500V transistor might have 2uS of storage delay. That is after doing everything I can think of to seed it up. About 4 years ago I switched to GAN MOSFETs and they are real fast.

 

Below is the modified circuit which varies the emitter resistor instead of the base resistor, to show a better comparison between unsaturated (green traces) and saturated (yellow traces) switching:
Note the lack of turn-off storage delay for the unsaturated case.