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Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!houxm!ihnp4!fortune!wall
From: wall@fortune.UUCP (Jim Wall)
Newsgroups: net.analog
Subject: Re: Big Capacitors
Message-ID: <4682@fortune.UUCP>
Date: Tue, 27-Nov-84 18:21:20 EST
Article-I.D.: fortune.4682
Posted: Tue Nov 27 18:21:20 1984
Date-Received: Wed, 28-Nov-84 04:39:35 EST
Reply-To: wall@fortune.UUCP (Jim wall)
Organization: Fortune Systems, Redwood City, CA
Lines: 21


	Ah, yes. Supercaps. Many companies make them now, with
Panasonic and NEC being the largest. They are perfect for CMOS
RAM back-up (months of backup up with just one supercap). A 
typical 1 farad capacitor at 5.5 volts is a 1 inch diameter 
cylender about .4 inches high.

	The physics of the cap is as follows. Early capacitors
stored charges between plates of material. Large caps took large
plates and rolled them into tight cylinders. This worked O.K. but
the surface area was still small, and the larger the surface
area, the higher the capacitance. The supercaps cover smaller plates
with activated carbon particles. Each particle multiplies the surface
area of a portion of the plate by a large amount. A plate covered with
particles has a huge surface area, and hence a very high capacitance.

	I have NECs liturature on them so more info is available...

						-Jim Wall
					....!amd!fortune!wall