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From: jjr@ut-ngp.UUCP (Jeff Rodriguez)
Newsgroups: sci.electronics
Subject: Choosing Cap Size in Power Supply
Message-ID: <5705@ut-ngp.UUCP>
Date: Sun, 26-Jul-87 22:39:35 EDT
Article-I.D.: ut-ngp.5705
Posted: Sun Jul 26 22:39:35 1987
Date-Received: Mon, 27-Jul-87 03:46:07 EDT
Reply-To: jjr@ngp.UUCP (Jeff Rodriguez)
Organization: Dept. of Elec. Engr.; Univ. of TX at Austin
Lines: 11


I'm building a general-purpose power supply based on 
a 12 V/450 mA transformer.  The secondary feeds into 
a full-wave bridge rectifier, which feeds into an 
LM317T adjustable voltage regulator (1.2 V to 27 V 
output at 1.5 A).

How do I choose the size of capacitor to place across 
the output of the rectifier?  I once heard that the 
rule-of-thumb is 1000 micro-F per 1 A of current.  
Is that reasonable?