From: Jim Thompson
Subject: Re: Transistors circuits by the thousands
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Date: Wed, 01 Jan 2003 22:35:13 GMT
NNTP-Posting-Date: Wed, 01 Jan 2003 17:35:13 EST
Organization: Cox Communications
On Wed, 01 Jan 2003 22:24:29 GMT,
In Newsgroup: sci.electronics.design,
Entitled: "Transistors circuits by the thousands",
Wrote the following:
|I'm looking at the datasheets for a 2n3904. It specifies an hfe of at
|least 20 at ic=.1ma. 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
|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
|Your comments would be appreciated.
Didn't you pose this question before?
At what current are you operating the 2N3904? The Beta peak for a
2N3904 is around Ic=11mA.
If the operating current is less than that, choose a smaller device.
BTW, It is bad design practice to be particularly sensitive to actual
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice:(480)460-2350 | |
| Jim-T@analog_innovations.com Fax:(480)460-2142 | Brass Rat |
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