[SI-LIST] : ESR and Q factor

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From: Chris Cheng (chris.cheng@3pardata.com)
Date: Thu Sep 21 2000 - 15:08:10 PDT


dear friends,
     this is a strange one. i am using a linear regulator to
generate 3.3V on one of my board. the app note calls out using
a 10uf tantalum for output stability. being a simple minded
person, i decided to use a 10uf ceramic cap instead, thinking
it has a better esl and esr value. to my surprise, the
output breaks into huge oscillation. when i switch back to
using tantalum caps, the output quiet down instantly. the
same can be achieve if i use a >1 ohm resistor in series
with the ceramic cap.
    the question is, has anyone experienced similar sensitivity
in dc linear regulators (the part is lineartech lt1086)? why
do linear regulator has such sensitivity to q factors ?
    thanks in advanced.
    chris

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