Path: utzoo!attcan!uunet!lll-winken!lll-tis!helios.ee.lbl.gov!pasteur!ames!oliveb!sun!david
From: david@sun.uucp (David DiGiacomo)
Newsgroups: sci.electronics
Subject: Re: 7805 regulator
Message-ID: <56936@sun.uucp>
Date: 17 Jun 88 02:45:52 GMT
References: <592@picuxa.UUCP> <5030002@hpvcla.HP.COM> <22117@amdcad.AMD.COM>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 21

In article <22117@amdcad.AMD.COM> phil@amdcad.UUCP (Phil Ngai) writes:
>In article <5030002@hpvcla.HP.COM> johne@hpvcla.HP.COM (John Eaton) writes:
>>< I have a question about the MC7805 5V 1A regulator. Can you parallel
>>< two of these devices together to derive a higher current?
>>In a word, NO. Unless they are extremely well matched then one will wind up
>>with most of the load and the other will have very little. The best way is
>
>I had a friend in college do this. I was skeptical but it worked fine. 
>
>What is the problem with one taking most of the load? They are over
>current and temperature protected anyway.

They are not protected from reverse current into the output.  I have
personally blown them up by wiring them backward.  Even hanging a BFC
("big capacitor") on the output can be bad news; you are supposed to have
a reverse diode across the regulator to discharge it.

What is the problem with buying a 323K or the new wave 5A/10A versions?

P.S. I'm sure there is more than anyone would ever want to know on this
subject printed on fine quality newsprint in the National regulator
handbook.