How can i know the current gain of transistor fom its data sheet?

[tefavolc]

how can i know the current gain of transistor fom its data sheet??

when i open a datasheet for a certain transistor i find a relation between Ic and Hfe at a certain Vce (ex Vce=4 volt), did this relation only correct at that Vce ? and if its that how can i calculate the Hfe for a certain Ic at any other value of Vce ? ?
i attach a data sheet for example

 

[uart]

First you should know that Hfe will vary from one transistor to the next, even if it's the same type (eg tip31A), that's why the datasheet lists "typical' values.

Additionally, for any given transistor, Hfe will also vary as a function of temperature, as a function of collector current, and as a function of Vce.

The variation of Ic/Ib with collector voltage is large as you approach saturation but not so large for bigger values of Vce.

So to answer to your question, the value of Hfe given at Vce=4 volts will remain approximately constant for a range of Vce values, provided Vce stays greater than about a volt more than Vce_sat (and of course less than the Vce breakdown voltage).

 

[Bob S]

Note that the DC current gain plotted in Fig.1 of your transistor is plotted at a V_ce that maximizes current gain.

Bob S

 

[tefavolc]

thnx for replaying