Dc current gain of bd139 transistor

Using Arduino General Electronics
#1

i have bd 139 transistor whose h[fe] is given as min-40 and max-250. I need to calculate values to drive dc motor. Which value should i take into consideration minimum or maximum.
Is h[fe] and current gain (beta) same thing?
Further i read somewhere that the gain of transistor cannot be greater than 100 i.e. the collector current can be maximum 100 mA when the base current is 1 mA. Is that true? how is it not true in case of bd139?

bd139 datasheet
http://pdf.datasheetarchive.com/indexerfiles/Datasheet-01/DSA00650.pdf

#2

bd 139 datasheet -http://pdf.datasheetarchive.com/indexerfiles/Datasheet-01/DSA00650.pdf

i could not figure it out

#3

Me neither. In the pdf file that you linked is not enough information. Try another datasheet. Click on the blue button "Download Datasheet", http://www.fairchildsemi.com/pf/BD/BD139.html In Figure 1, you see the current gain at a certain collector current. For example at 500mA, the gain is 80.

#4

Neither is appropriate - you need to know what base current causes saturation (for a particular collector current). For many old transistors like this the base current for saturation is 10% of collector current or more even.

Use a MOSFET if you can, much easier to drive.

#5

i have a transistor whose gain at 0.15 amp collector current is given as minimum : 40 maximum :250

I am using the transistor for my project so how to calculate base current. the transistor is bd139

#6

Use worst case, 40. If you need 150mA for Ic, 150/40=3.75mA Ib

#7

@zammikao, please stop cross-posting.

#8