how to find beta given minimum=40 , maximum = 120...
Ic = 150 mA , Vce=10V ...how can i find the beta , and if the specific beta is found will the Ic and Vce values change.?

 

Can you be a bit more specific about your exercise? It would be ideal if you posted it.

Theoretically, you can find the value of beta, with Ic and Vce known, from a corresponding graph like the following, but which is specific to each model of BJT.
You find the corresponding value of Ib, and the use the equation Ic=b*Ib.

 

You said that the minimum beta is 40 and the maximum beta is 120.
But you want to know the beta at 150mA and 10V.
The datasheet has a graph of "typical" beta but you can't buy a transistor with "typical" beta because some are low and some are high as in the first sentence.

A transistor circuit can be designed so that a transistor with a low beta or a transistor with a high beta makes little difference. But some people design a circuit that works only with one beta number then many circuits won't work.

 

Can you be a bit more specific about your exercise? It would be ideal if you posted it.

Theoretically, you can find the value of beta, with Ic and Vce known, from a corresponding graph like the following, but which is specific to each model of BJT.
You find the corresponding value of Ib, and the use the equation Ic=b*Ib.

It is actually specific to each individual transistor, not just each model. Perhaps this is what you meant, as I'm pretty sure you know this.

 

It is actually specific to each individual transistor, not just each model. Perhaps this is what you meant, as I'm pretty sure you know this.

Well, you have to start somewhere. If you want to make use of the above chart, you have to accept it as a good description of your current transistor model.

How do you suggest of making use of such a diagram? Building a new, correct diagram for each transistor by taking measurements?

 

You should never use a simplified model of a transistor to learn how to bias one. Then the hFE is a certain number and not a range of numbers and the Vce is also a certain number not affected by temperature.

A student would simply bias a transistor with a single resistor from the positive supply and not use an emitter resistor. Then the transistor is a thermometer instead of an amplifier.

 

Hey, I am a student too, even though many people in the forum seem to forget it, so don't think too highly of me.

I know that simple biasing techniques are only for educational purposes. My question was if the Ic-Vce chart has any useful information for implementation purposes.

 

Hey, I am a student too, even though many people in the forum seem to forget it, so don't think too highly of me.

I know that simple biasing techniques are only for educational purposes. My question was if the Ic-Vce chart has any useful information for implementation purposes.

If it's typical data, then no. Minimum beta is about the only useful beta data (I'm a poet!) point for reliable linear circuit design, and even that is almost useless for designing saturated switches. Most transistors will prescribe that saturation voltages are specified for Ic/Ib=10, and occasionally, 20.
The V-I curves are helpful in getting an understanding of how transistors work, but not for circuit design.