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From: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
Newsgroups: rec.railroad,sci.electronics
Subject: Re: Thyristors
Message-ID: <1831@bloom-beacon.MIT.EDU>
Date: Wed, 18-Nov-87 10:16:21 EST
Article-I.D.: bloom-be.1831
Posted: Wed Nov 18 10:16:21 1987
Date-Received: Sat, 21-Nov-87 04:23:14 EST
References: <3226@aw.sei.cmu.edu> <3165@husc6.UUCP> <4948@sdcrdcf.UUCP> <2236@ihuxv.ATT.COM> <1152@gilsys.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: wolfgang@mgm.mit.edu (Wolfgang Rupprecht)
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Organization: Independent Software Consultant
Lines: 15
Keywords: mechanism of operation
Xref: mnetor rec.railroad:948 sci.electronics:1761

In article <1152@gilsys.UUCP> mc68020@gilsys.UUCP (Thomas J Keller) writes:
>   A triac is essentially two SCRs back to back, with their gates connected
>together.

This is true in the same spirit as a transistor is just two diodes
hooked back to back.

An SCR is a 4-layer device (p-n-p-n) and a TRIAC is a 5-layer device
(p-n-p-n-p). One can't fully describe a triacs 4-quandrant operation
(gate vs.  anode voltage polatity) by modeling it as 2 SCRS. That
would only account for 2 quadrants of operation. Any basic electronics
text can clear up these mysteries.
Wolfgang Rupprecht	UUCP: mit-eddie!mgm.mit.edu!wolfgang
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