Subject: Re: Transistors circuits by the thousands
Date: Tue, 07 Jan 2003 22:24:52 +0100
Organization: Wanadoo, l'internet avec France Telecom
NNTP-Posting-Date: 7 Jan 2003 21:24:53 GMT
X-Mailer: Mozilla 4.79 [en] (X11; U; Linux 2.4.20 i686)
> Hi Guru's
> I'm looking at the datasheets for a 2n3904. It specifies an hfe of at
> least 20 at ic=.1ma.
Actually, it depends on the manufacturer of the 2n3904. The datasheet
from ST (www.st.com) specifies hfe min of 60 at Ic=0.1mA, Vce=1V,
@Tcase=25°C (hfe will fall with temperature; hfe mix peaks at 100, for
> The "typical" performance curve show a gain of
> I need the hfe to be at least 50.
> If I was designing a circuit to be manufactured by the thousands, how
> risky would it be if I do not use worst case values? Am I really
> likely to end up with a batch of transistors that stray far from the
> "typical" values.
> My alternative is to use another transistor (more cost, higher parts
> Does anyone have experience with this? Do you always use worst case
> values for high volume designs? I've looked at designs from far east
> manufacturers and they often seem to get away with simply using
> "typical" specs.
> Your comments would be appreciated.