> Got it. I was confused with cut off frequency ( not -3 db ) The -3dB point is often called the "cutoff frequency", although I prefer the term rolloff frequency. The former implies a sudden transition, which this certainly is not. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads