Chip McDonald Posted March 18, 2001 Share Posted March 18, 2001 Hey Craig - Just finished reading your article on DC offset - nice straight forward explanation.... What exactly is the process of an opamp being "laser trimmed"? I understand the process of a "trim" pot adding an inverted counter-voltage, but what/how is the process involving a laser and the manufacture of opamps makes this unneccessary? http://www.mp3.com/chipmcdonald This message has been edited by Chip McDonald on 03-18-2001 at 03:22 PM Guitar Lessons in Augusta Georgia: www.chipmcdonald.com Eccentric blog: https://chipmcdonaldblog.blogspot.com/ / "big ass windbag" - Bruce Swedien Link to comment Share on other sites More sharing options...
Ethan Winer Posted March 19, 2001 Share Posted March 19, 2001 Chip, > What exactly is the process of an opamp being "laser trimmed"? I understand the process of a "trim" pot adding ... < Laser trimming does exactly the same thing. But instead of a physical variable resistor (trimpot), two fixed resistors are used. One is then burned with a laser beam to change its resistance until the DC offset is at a minimum. This method avoids yet another mechanical device that can (read: will) go bad eventually, or drift out of adjustment. --Ethan The acoustic treatment experts Ethan's Audio Expert Book Link to comment Share on other sites More sharing options...
Anderton Posted March 19, 2001 Share Posted March 19, 2001 ...and there you have it! Thanks Ethan. One more thing...I mentioned the example in the EQ article of the waveform being transposed so low it created a varying DC offset. I suppose one could nitpick whether a varying DC offset is really just a low-frequency AC offset, but I think it's more realistic to think of something that low in frequency (e.g., sub-subsonic) as being closer to DC than AC. Craig Anderton Educational site: http://www.craiganderton.org Music: http://www.youtube.com/thecraiganderton Twitter: http://www.twitter.com/craig_anderton Link to comment Share on other sites More sharing options...
Ethan Winer Posted March 19, 2001 Share Posted March 19, 2001 Craig, > I suppose one could nitpick whether a varying DC offset is really just a low-frequency AC offset < Either way it impinges on the headroom! --Ethan The acoustic treatment experts Ethan's Audio Expert Book Link to comment Share on other sites More sharing options...
Chip McDonald Posted March 19, 2001 Author Share Posted March 19, 2001 "Ah!" Craig, Ethan - Thanks.... http://www.mp3.com/chipmcdonald Guitar Lessons in Augusta Georgia: www.chipmcdonald.com Eccentric blog: https://chipmcdonaldblog.blogspot.com/ / "big ass windbag" - Bruce Swedien Link to comment Share on other sites More sharing options...
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