It would not be needed if the devices were perfect. Consider the output of a voltage regulator. An electrolytic will moderate the slower glitches due to load swings while a smaller ceramic device will damp any tendency to oscillate. Each of the capacitors will have enough inductance to oscillate at some frequency, hopefully the pair will yield a more ideal function. Worst case, the circuit oscillate on both frequencies. Fortunately, this is not the usual outcome. John Ferrell 6241 Phillippi Rd Julian NC 27283 Phone: (336)685-9606 johnferrell@earthlink.net Dixie Competition Products NSRCA 479 AMA 4190 W8CCW "My Competition is Not My Enemy" ----- Original Message ----- From: "Jamie Jensen" To: Sent: Thursday, November 06, 2003 8:24 AM Subject: [EE]:Capacitors (basic question) > Not being an EE by education..... > > I always thought capacitors as simple bulk storage devices, use some big ones to filter out the ripple on power supplies and bunches of lil ones on chips for adding the last "umph" when they switch and draw more current. > > But ive seen and read stuff about using a mix of big and small for better frequency response. But can someone explain exactly what that means? If you have a circuit running at 20 MHz do you need to worry about a cap that responds at 100MHz? I just am not so clear on this (frequency response of a cap). Sorry if this is too basic of a question. > > -JJ > > > --------------------------------- > Do you Yahoo!? > Protect your identity with Yahoo! Mail AddressGuard > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body