I agree - ALL semiconductor demodulate. If they did not then there would be NO distortion in amplifiers and most of the HiFi industry would be out of business.
Demodulation is only part of the problem however. Consider a semiconductor switching a relay. The semiconductor may switch the relay due to external EMC - but it is more likely that the semiconductor or the relay will fail and produce an 'unsafe' output. I spent 6 months designing a fail-safe synchronous gating circuit and 3 months writing the patent so Please don't tell me that it is impossible to design a safe circuit. In my experience (20 years of R&D) spurious EMC/safety issues are mostly due to poor design, in the first place, and then inadequate testing. EXAMPLE from the last 10 years - when the 5Volt PSU for a safety circuit was disconnected, the system was ARMED. This was discover just before the product went into production and after "through"(sic) testing. Best regards Gregg PLEASE NOTE NEW NUMBERS P.O. Box 310, Reedville, Virginia 22539 USA Phone: (804) 453-3141 Fax: (804) 453-9039 Web: www.test4safety.com -----Original Message----- From: [email protected] [mailto:[email protected]]On Behalf Of Cortland Richmond Sent: Friday, January 04, 2002 12:54 PM To: [email protected] Cc: [email protected] Subject: Re: EMC-related safety issues I don't believe this is what people are saying here. What they are saying is, ordinary semiconductors won't demodulate RF levels produced by an unintentional radiator. Cortland (What I write here is mine alone. My employer does not Concur, agree or else endorse These words, their tone, or thought.) [email protected] wrote: Does anyone else think that ordinary semiconductors doesn't respond to RF? I have tested a product which was little more than an LM324 quad op-amp for RF immunity using IEC 61000-4-3. This op-amp has a slew rate of 1V/micro-second on a good day with the wind in its favour. It was housed in an unshielded plastic enclosure. Demodulated noise that exceeded the (not very tough) product specification were seen all the way up to 500MHz at a number of spot frequencies that appeared to be due to the natural resonances of the input and output cables. ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: No longer online until our new server is brought online and the old messages are imported into the new server.
