DC offset question...
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 Chip Amps Amplifiers based on integrated circuits

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 11th May 2012, 09:12 PM #1 marcus1 diyAudio Member   Join Date: Jul 2004 DC offset question... Apologies if this has been asked before but I've searched dozens of posts but can't find anything regarding measuring my DC Offset question that I understand so.... To find out the DC offset of a chip-amp itself (a LM4780) is it possible just to put a 10 ohm(?) resistor across signal/earth of the input rca plugs and measure the DC offset from the amp output? Or is there more to it than that? - I thought the only thing that may change the amps DC offset (with the input connected) was if there was any DC on the signal going into the amp. Thanks
 11th May 2012, 09:49 PM #2 richie00boy   Did it Himself diyAudio Member     Join Date: Nov 2003 Location: Gloucestershire, England, UK Your method is fine. Even if there was DC on the source, the input capacitor on the chip amp will block it. Unless you didn't fit the capacitor... __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, modules and more.
 11th May 2012, 09:56 PM #3 ChicagoJTW diyAudio Member   Join Date: Mar 2011 I've always just shorted the input and measured from the speaker output terminals (no speakers connected). That won't give the chip's offset per se, but the offset for the amplifier's entire circuit.
 12th May 2012, 10:37 AM #4 AndrewT   diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders The dummy Rs fitted to the input can be chosen from 0r0 to 1M0. The output offset and output noise results will be different over than enormous range of RS. Useful information about the amplifier performance can be gleaned by looking at a range of Rs, rather than just shorting the input with Rs=0r0. __________________ regards Andrew T.

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