Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2.fluke 9/24/84; site fluke.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxj!houxm!vax135!cornell!uw-beaver!ssc-vax!fluke!tonjon From: tonjon@fluke.UUCP (Tony Johnson) Newsgroups: net.analog Subject: Re: The difference between capacitors and batteries Message-ID: <133@vax2.fluke.UUCP> Date: Tue, 11-Dec-84 14:30:41 EST Article-I.D.: vax2.133 Posted: Tue Dec 11 14:30:41 1984 Date-Received: Fri, 14-Dec-84 06:01:43 EST References: <158@decwrl.UUCP> Organization: John Fluke Mfg. Co., Inc., Everett, WA Lines: 36 > > A battery is an extremely nonlinear capacitor. This is due to > the fact that the charge changes the characteristics of the dielectric. > Period. They optimize difference aspects of similar phenomenon. You will > find that all capacitors are somewhat nonlinear. Vendors tend to stuff > this characteristic into the absolute tolerance. Polystyrene and > polypropalene ( spelling? ) tend to be the most linear. Batteries are > the most nonlinear. You don't find many that are inbetween until you > get to solid state capacitors processed in silicon, where the depletion > layer varies with charge. The development of linear capacitors in IC's > was a major breakthrough for systolic arrays and switched capacitor > networks. It should be noted the the nonlinearity in silicon is inverse > to the nonlinearity you find in batteries. > > ----{ john williams }---- I have a question as to what we're talking about when we say 'non- linear'...nonlinear as a function to what; frequency, applied voltage, time? Polystyrene and 'polypros' have great performance with respect to a phenonmenon called dielectric absortion i.e., they don't 'soak' as much as say mylar or (yeech) electrolytic. That's why they're great for use in integrating A/D converters. But if one is concerned about nonlinear performance with respect frequency i.e. 'hook', NPO ceramics perform very well. A few references: Horowitz, Paul and Hill, Winfield; 'The Art of Electronics'; pg 18-19; Cambridge University Press; Cambridge, 1980. Pease, Robert A.; 'Understand capacitor soakage to optimize analog systems'; EDN, 13 October, 1982. Johnson, F.L.; 'Technical Bullitens 1-10'; Electrocube Corp.. You can probably get this stuff from the local Electrocube rep. Tony Johnson John Fluke Mfg. Co. Inc. Everett, WA