From: Jim Thompson
Subject: Re: FET transistion frequency parameters
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Date: Wed, 04 Dec 2002 18:48:20 GMT
NNTP-Posting-Date: Wed, 04 Dec 2002 13:48:20 EST
Organization: Cox Communications
On Wed, 04 Dec 2002 08:12:23 -0800,
John Larkin ,
In Newsgroup: sci.electronics.design,
Entitled: "Re: FET transistion frequency parameters",
Wrote the following:
|On Wed, 04 Dec 2002 08:08:33 +0000, Paul Burridge
|>One of my reference books gives all the data on hundreds of different
|>types of FETS and BJPs. However, I've just noticed that the column for
|>Ft is simply left blank in respect of every device that's listed as a
|>FET. Why isn't transition frequency data published for these devices??
|Ft is the current-gain-bandwidth product, the frequency where bipolar
|transistor Hfe (beta) drops to unity. That's meaningless for a fet.
The critical parameter for gain-bandwidth of CMOS is gmC.
For analog applications I evaluate a CMOS process by biasing a
diode-connected CMOS device with a current source, and insert my
LoopGain part (see my website) between the drain and gate.
I then do GBW simulations (.AC) with varying bias currents.
When evaluating for digital applications just make a ring oscillator
and then vary the sizes.
| 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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