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From: jfw@ksr.com (John F. Woods)
Newsgroups: sci.electronics
Subject: Re: Voltage Regulators in Parallel
Message-ID: <3608@ksr.com>
Date: 17 May 91 17:05:57 GMT
References: <1991May16.165916.12600@tc.fluke.COM>
Sender: news@ksr.com
Lines: 16

ferguson@tc.fluke.COM (Ed Ferguson) writes:
>I'm adding voltage regulation to my audio amp to improve performance.
>Vout is +/- 28 V and the amp draws 3A on each peak.  National makes an 
>adjustable 3A positive regulator (LM150) but I don't see a 3A negitive
>adjustable regulator offered.
>Could two LM317Ts (1.5A each) and two LM337Ts (1.5A each) operate in
>parallel to supply the +/- rails at 3A?  Or is a regulator with
>a series pass transistor the better way to get more current?

First, the LM145 is a 3A negative adjustable regulator.  You can't just
wire regulators in parallel, they don't share well; it is fairly simple to
devise a circuit which makes them share better, but the regulation probably
suffers (the data book isn't clear on the behavior of the circuit, but it
looks fishy to me).  A pass transistor is probably the way to go; use the
right circuit and it will even benefit from the current limit built into 
the regulator.