so in my case for saturation IB should be 1mA ...right?more base current is needed for saturation - the definition of saturation is when Vce is < Vbe
so for saturation - you need more Ib ....
There's no harm in putting in too much base current..
No. You will NOT drive the transistor into saturation. This was already explained.long as you can spare the mA from your supply rail.
Just make sure you give at least Ic/beta for base current.
Okah that'S nice,...I got it.Beta is used for calculating the linear biasing conditions of the transistor, it is not for determining the base current for transistor operation as a saturated switch, as many beginners try to do.
As has been stated, the base current for saturated operation is typically 1/10th of the maximum collector current.
Ohhhkakkkk. It means if i want IC= 10mA,,,,then with the rule of thumb, IB =1mA,,,,so for IB=1mA ,,,i have to choose VCE(Sat).Rule of thumb used by many is Ib = Ic / 10 to get the transistor fully
saturated. Its called forced beta. 2N3904 for example
View attachment 175330
Regards Dana.
Okah so I got it....Okah that'S nice,...I got it.
So for the above transistor which I mentioned, if I have to calculate Rc = (VCC-VCE(sat))/IC,,,,, where VCC is 10V and Ic, i want 10mA,,, now the VCE(sat) will be 0.2V or 1V(as per the datasheet) ....for VCE(sat)which value should I choose.....
or any other calculation to find VCE(Sat) and then RC.....
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Ohhhkakkkk. It means if i want IC= 10mA,,,,then with the rule of thumb, IB =1mA,,,,so for IB=1mA ,,,i have to choose VCE(Sat).
am i right?
if yes, then VCE (sat) can be get graph from datasheet...
Yes excatly. The current can be regulated by the Rc value. transistor is just as a switch.If it's not clear, the saturation collector current is determined by the collector load impedance, not the transistor itself.
The transistor is being used as the contacts of a switch so, just like the contacts of a relay, the current is determined by the load, not the contacts.
Well as we earlier discussed,,,Yes i agree.
What would be interesting to know would be, for the case of a 2N3904 (in common emitter connection) with 10k collector resistor to a 5v rail.....what exact base current would need to flow to just about give saturation?.....just right on the edge of saturation?
I actually think that this current is not exactly knowable.......the OP has raised an excellent question....its simply unknown
How often do we need to say that Beta has little to do with saturation voltage, until you understand?if you have IC then from the datasheet you will have ß also...so you can calculate IB
Yes I got it. I read some more notes. Basically once the transistor is in saturation, no matter you how far base current you inject after this.@cupoftea @parth22 You guys are TOTALLY ignoring everything that people have been TRYING to tell you.
1) Beta has nothing to do with saturation voltage. Again, BETA HAS NOTHING TO DO WITH SATURATION VOLTAGE. By definition, when a BJT is in saturation an increase in base current causes no change in collector current.
2) If you read the data sheet you will see that the value for beta (hfe) has a HUGE range. In fact, they only specify minimum and typical; there’s no maximum. Knowing Ic will not enable you to calculate Ib ’exactly’.
3) This is why transistors use feedback to set gain.
4) Reading the data sheet will also tell you typical Ib for typical Vce-sat at a particular Ic.
This is cupoftea, formerly known as treez, always known as a willfully ignorant poster.How often do we need to say that Beta has little to do with saturation voltage, until you understand?
This is beginning to seem like a troll.
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