From: Jim Thompson
Subject: Re: Transistor current gain with temperature
References: <3D944E62.AE8D71CC@hotmail.com> <3D94633C.363EC763@kth.se>
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Date: Fri, 27 Sep 2002 15:25:35 GMT
NNTP-Posting-Date: Fri, 27 Sep 2002 11:25:35 EDT
Organization: Cox Communications
On Fri, 27 Sep 2002 15:55:08 +0200,
Uwe Zimmermann ,
In Newsgroup: sci.electronics.design,
Entitled: "Re: Transistor current gain with temperature",
Wrote the following:
|Tom Sharp wrote:
|> Does anyone know the minimum current gain of a BC817-16 @ -40 degrees C
|> with 1mA collector current?
|Transistor gain is higher at lower temperatures, however, -40C shouldn't
|have a too strong influence. Therefore I would assume the minimum
|current gain to be only slightly above the minimum current gain at room
|According to the datasheet of the BC817-16 at onsemi.com, the current
|gain at Ic=1mA is about a factor 3 below the value at Ic=100mA stated as
|Alltogether I would strongly expect the minimum current gain at 1mA and
|-40C not to be below 30.
Wrong! BIPOLAR Gain is lower at low temperatures and higher at high
temperatures. A loose rule of thumb I use when designing I/C's is
that gain (beta) at -55°C is 1/2 of the gain at 27°, and the gain at
125°C is twice that at 27°C.
The only "beta" curve I see in the ON Semi data sheet is beta versus
current... it's a very large device thus performs poorly at low
currents (ISE for those of you interested in modeling; the high end
roll off is due to IKF).
| 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 |
| http://www.analog-innovations.com | 1962 |
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