[andyr]

A mate of mine who designs amplifiers for a living, designed an emitter-follower regulated PS 15 years ago, which I have used to power my active XOs and my phono stage.

I was talking to someone recently (who may or may not know what he is talking about!     ) who said the BD139 is an old design and I should use a more modern transistor which has a faster slew rate.

So can anyone advise me which transistor would meet this criterion (and be able to output 150-200 milliamps)?


Thanks,

Andy

[*Scotty*]

From the data sheet the Transition frequency(fT) is 190MHz. The guaranteed beta on a BD139-16 which is a selected part 200. There may be a newer faster part out there but do you really need over a 190MHz bandwidth.
http://www.utc-ic.com/uploadfile/2011/1012/20111012023505473.pdf
Onsemi and Fairchild can supply high beta BD139-16 transistors.
Scotty

[andyr]

From the data sheet the Transition frequency(fT) is 190MHz. The guaranteed beta on a BD139-16 which is a selected part 200. There may be a newer faster part out there but do you really need over a 190MHz bandwidth.
http://www.utc-ic.com/uploadfile/2011/1012/20111012023505473.pdf
Onsemi and Fairchild can supply high beta BD139-16 transistors.
Scotty

Thank you, Scotty.  As I wrote ... I wasn't sure whether this person knew what he was talking about ... and it appears he didn't!! 

I shall relax. 

Regards,

Andy