Post by thread:[EE:] is it possible to get 0.01uF with polarity?

I have seen RF caps of around this value which have an "earth" marked at one end (& which corresponds to the outermost film) but not polarised caps. RP On 29/01/07, Tal Go <spam_OUTtalgoTakeThisOuTusb.co.il> wrote: > Hello to all > > I found in some schematics on the 'net a 0.01uF capacitor with polarity. I > must admit that I didn't heard about this component, can anyone point to a > web site that I can see a capacitor like that? > > Thanks > > Tal > > -

On Mon, 29 Jan 2007 01:45:09 +0200, you wrote: >Hello to all > >I found in some schematics on the 'net a 0.01uF capacitor with polarity. I >must admit that I didn't heard about this component, can anyone point to a >web site that I can see a capacitor like that? I suspect it is just lazy schematic drawing, using the same symbol. The lowest value polarized cap I've seen os a 0.1uf tantalum bead. AFAIK there are no electrical advantages in using a polarised cap over a non-polarized one - at larger sizes they are used for their size and cost advantages, although ceramics have been pushing up the typical cross-over point in recent years, especially in performance-sensitive areas like DC/DC converters where ceramics of 10uf and higher are commonplace.

maybe describe the circuit or if you have a schematic.....might be easier to determine if it really needs a polorized cap? So, if what Mike says is true...and I pretty much agree since caps are just plates with dielectric seperation...why do tantalums blow if inserted backwards (ive seen the results) Mike Harrison <.....mikeKILLspam@spam@whitewing.co.uk> wrote: AFAIK there are no electrical advantages in using a polarised cap over a non-polarized one - at larger sizes they are used for their size and cost advantages, although ceramics have been pushing up the typical cross-over point in recent years, especially in performance-sensitive areas like DC/DC converters where ceramics of 10uf and higher are commonplace. --------------------------------- Sucker-punch spam with award-winning protection. Try the free Yahoo! Mail Beta.

Mike didn't say that capacitors shouldn't have polarization, he simply said that if you have a polarized cap and an unpolarized one with similar characteristics, there is no electrical reason to choose one over the other. The reason polarized caps fail in reverse is due to the composition of the cap. The breakdown voltage in one direction is much lower than in the other direction due to the two (usually different types) of films/materials used for each electrode, and the dielectric inbetween. The charge carriers work well when the electrons congregate on one film, and not so well with the electrons form on the other plate. They are popular because the composition allows for a higher capacitance in a smaller area - among other reasons. -Adam On 1/29/07, alan smith <micro_eng2KILLspamyahoo.com> wrote: {Quote hidden}> maybe describe the circuit or if you have a schematic.....might be easier to determine if it really needs a polorized cap? > > So, if what Mike says is true...and I pretty much agree since caps are just plates with dielectric seperation...why do tantalums blow if inserted backwards (ive seen the results) > > Mike Harrison <.....mikeKILLspam.....whitewing.co.uk> wrote: > > AFAIK there are no electrical advantages in using a polarised cap over a non-polarized one - at > larger sizes they are used for their size and cost advantages, although ceramics have been pushing > up the typical cross-over point in recent years, especially in performance-sensitive areas like > DC/DC converters where ceramics of 10uf and higher are commonplace. > > > > > --------------------------------- > Sucker-punch spam with award-winning protection. > Try the free Yahoo! Mail Beta. > -

Their schematic is using an electrolytic cap, but as others have said, it shouldn't be critical if you use a non-polarized cap as a replacement. The thing you must consider is what voltage the cap will be exposed to, and then refine your search for a 0.01uF cap at the appropriate voltage rating. If you don't mind, could you reply with a link to the schematic in question? Thanks, Bill --- Tal Go <EraseMEtalgospam_OUTTakeThisOuTusb.co.il> wrote: {Quote hidden}> Hello to all > > I found in some schematics on the 'net a 0.01uF > capacitor with polarity. I > must admit that I didn't heard about this component, > can anyone point to a > web site that I can see a capacitor like that? > > Thanks > > Tal > > --

Hi all.. The reason I notice the cap polarity was non working NE555 one-shot circuit. so I look for more info to see what is wrong, then I saw the cap polarity issue. at the begging I thought that the value of the cap is wrong but I check again in the datasheet and I began to suspect that maybe the authors did some trick to operate the on shot correctly with this bizarre cap... After my second look at the data sheet I notice that my problem was missing pull-up resistor on the trigger pin. with out it the output is going crazy :-) btw, here is the link that made this mess: http://www.utm.edu/staff/leeb/3b3.htm There are more links with this mistake but I didn't save it ...I think most of them use the same schematic program. Tal {Original Message removed}