newbi to transistor numbers and letters after

[kbyrne]

Can any body help a newbi to electronics with a clarification. I researched a part #
IRF9540 with Digi key and got the result of  manufacture part # IRF9540NPBF. how do tellif it will work as i have the sme problem with other transistors pluss TL084
OPAMPS. The letters at the und make me unsure weather to buy them or not and search for exact numbers.

 

[Hero999]

The parts are electrically identical, PbF just means lead free.