On Sat, 19 Jun 2004 01:34:26 +0200, Lindy Mayfield wrote: > > > >My problem is in understanding the function those components > > >in the diagram have from the PWM output to the op-amp. > > Specifically > > >what the relationship is between the PWM coming out from the > > PIC > > >and what is going on with the resistors and caps. > > > > That network of resistors and capacitors functions as a low-pass > > filter: it takes the high-frequency PWM signal and removes the > > AC > > components (or most of them, anyway, except for a little bit of > > ripple) from it, leaving only the DC component which represents > > the average value of the PWM waveform. > > > > Dave D. > > > > > I remember LPF's and HPF's from studying about synthesizers. Like, for instance, passing a noise through it and getting a cymbal or drum sound. > > But you mention DC components. I don't understand that. What does that have to do with the DC PWM signal? Where was the AC in the mix? > > And most importantly, why or what about the PWM signal made it necessary to low-pass-filter it? What where they trying to get by it? A PWM signal generates a high frequency signal and the low pass filter removes those high frequency components to make a smooth wave. Maybe read up on Fourier series to understand the relationship between square waves and sine waves: http://www.geocities.com/ac_dc_ac/FourierEng.html http://cnx.rice.edu/content/m10687/latest/ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body