On 7/20/2011 9:55 AM, V G wrote: > On Wed, Jul 20, 2011 at 9:46 AM, Joe Wronskiw= rote: > >> I'm not very up on the theory, but it has to do with phase shift and >> gain at different frequencies. The cap cuts down the high freq gain to >> suppress the oscillation. Michael W's suggestion about the input R is >> related to the same principal, I think. This is an area that makes me >> wish I had read more of Bob Pease's articles, but of course they're >> archived somewhere. The general topic is "compensation" Most op amps >> used to have an input pin for this, as well as 2 other pins for offset. >> > I thought about it for 5 minutes, and I'm going to take a wild guess here= .. > > The small valued capacitor acts as a "short" for very high frequencies an= d > therefore allows the passage of those frequencies into the negative input > and subsequently causes their increased suppression. > > Increasing the value of the capacitor (to 10uF, for example), allows lowe= r > frequencies to be suppressed more (which is undesirable in this case). > > Does that make sense? Or am I totally off? That is the way I generalize op-amp circuits. John G's link to the TI=20 pdf should be an excellent reference to more detailed explanations. It=20 should also help you decide whether the LT1028 is right for your=20 application. --=20 Joe Wronski Stillwater Embedded Engineering www.stillwatereng.net --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .