Date: Fri, 6 Nov 92 10:31:33 EST From: peterca@ento.csiro.au Subject: Re: Small Value Film Caps >I am looking for extremely small film capacitors (in the 100-1000 pF range) >for use in stabilizing feedback loops in power amps. I don't want to use >the standard ceramic caps because I have had difficulties in the past with >small amounts of distortion and microphonics caused by piezoelectric effects. >Unfortunately, no very small film caps seem to be made, and I don't want to >string a number in series to reduce the value. Has anyone out there ever >seen such creatures for sale? Polypropylene or polyester would be fine, to >start out with anyway. I don't think you can get polypropylene this small but that is because you can use polystyrene which is what you would use instead of polypropylene if you could get them that big. IE polystyrene is readily availlable and as good as polypropylene and better than polyester. It has very low dielectric absorbtion and good stability which are supposed to correlate well with good sound. Ideally use an extended foil type which is designed for superior HF (radio frequency) performence. The foil is wound in a cylinder. If the leads are attached at one point there is some series inductance. In an extended foil the lead attatches accross the protruding edge of the wound foil thereby shorting out the windings of each "plate" of the capacitor. ---------------------------------------- Peter Campbell C/O Div. Entomology, C.S.I.R.O. Box 1700 Canberra A.C.T. 2601 Australia (peterca@ento.csiro.au) Ph.61-6-2464158 (w), 61-6-2516213 (h) ---------------------------------------- From: daver!cypress.com!ssr@decwrl.dec.com (Bapcha/FPGA) Subject: Re: Small Value Film Caps Date: Fri, 6 Nov 1992 01:48:41 GMT In article <1db92sINN8lb@uwm.edu> Scott Dorsey writes: > >I am looking for extremely small film capacitors (in the 100-1000 pF range) >for use in stabilizing feedback loops in power amps. I don't want to use >the standard ceramic caps because I have had difficulties in the past with You can get small value chip caps to 25 Volts. THey are also very small and nice to use (but difficult to solder). -Bapcha- -- Bapcha - A very bad boy from Cypress Semiconductor 3901 N. First Strasse San Jose, CA 95134, 408-943-2719 ------------------------------ From: oracle!us.oracle.com!on@uunet.UU.NET (On G. Paradise) Subject: Re: Small Value Film Caps Date: Fri, 6 Nov 1992 08:31:23 GMT kludge@grissom.larc.nasa.gov (Scott Dorsey) writes: >I am looking for extremely small film capacitors (in the 100-1000 pF range) >... >Unfortunately, no very small film caps seem to be made... Panasonic P-series (Polypropylene) begins at 100 pf. According to the catalog, these are similar to Roderstein KP-1835 and Wima FKP. Digi-Key: (800) 344 4539. Philips Passive Components have: 704C1 Polystyrene 47 pf and up 719C1 Polystyrene 100 pf and up 703E1 Polypropylene 47 pf and up Philips: (818)240 4880, (915)775 4242, (407)863 1800 or (808)772 2500. But watch out: Some film capacitors may be a bad choice for neutralizing stray capacitance at the inverting input. You want something that has low-Z beyond your voltage gain bandwidth. >--scott On From: haverl@cats.ucsc.edu (Carl A Haverl) Subject: Re: Small Value Film Caps Date: 6 Nov 1992 18:33:08 GMT Polyester is another name for mylar. Mylar capacitors are available at most electronic supply stores that service industry, i.e. any place other than Radio Shack. Most metropolitan areas have such an electronics distributor. Carl -- Carl Haverl haverl@cats.ucsc.edu 305 Chace St. Santa Cruz, CA 95060 (408) 458-3259