From: Jim Thompson
Subject: Re: FET transistion frequency parameters
References: <email@example.com> <0ksH9.371$Gg7.firstname.lastname@example.org>
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Date: Thu, 05 Dec 2002 00:29:53 GMT
NNTP-Posting-Date: Wed, 04 Dec 2002 19:29:53 EST
Organization: Cox Communications
On Wed, 4 Dec 2002 19:03:21 -0000,
"Kevin Aylward" ,
In Newsgroup: sci.electronics.design,
Entitled: "Re: FET transistion frequency parameters",
Wrote the following:
|Jim Thompson wrote:
|> On Wed, 04 Dec 2002 08:12:23 -0800,
|> John Larkin ,
|> In Newsgroup: sci.electronics.design,
|> Article: ,
|> 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.
|Nah....just make minimum size nmos/pmos inverter gain amp an see what
|its gain with frequency is over supply volts.
Some of us know better than to use inverters for analog gain... too
My method tests gain with (in essence) the same size device as a load.
| 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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