Re: difference between anode and cathode?

On Sat, 28 May 2005 14:59:00 -0400, John Popelish <jpopelish@xxxxxxxx>
wrote:

>Michael Noone wrote:
>> Hi - I thing the single thing that causes me the most problems with
>> electronic devices is polarities. Right now the thing that is really
>> bothering me is the difference between an anode and a cathode. According to
>> dictionary.com, an anode is:
>>
>> 1. A positively charged electrode, as of an electrolytic cell,
>> storage battery, or electron tube.
>> 2. The negatively charged terminal of a primary cell or of a storage
>> battery that is supplying current.
>>
>> What got me confused is that I had always thought cathodes were positive -
>> but then I was reading that the end pointed to by the triangle in a diode
>> is the cathode, and since the triangle denotes the current flow - that
>> means current flows from the anode to the cathode in a diode. So - can
>> somebody please help me out a bit here?
>
>Think conventional current (the flow of positive charge) not the
>movement of electrons.
>
>> On a related note - is there any standard in which lead in a polarized
>> component is positive and which is negative? (ie electrolytics, tantalums,
>> leds, etc.)
>
>There are several. ;-)
>Some are marked with a "+" and some are marked with a "-". Some film
>capacitors have a strip at one end, but this indicates the lead
>connected to the outer wrap of foil that acts as a shield for the rest
>of the capacitor. I think most polarized capacitors for through hole
>mounting also have a short lead, usually indicating the more negative
>terminal. LEDs usually have a small flat spot on a ring around the
>case and a short lead that indicates cathode, but I just found an
>exception to that. If in doubt, check the data ***.

Skyworks makes some surface-mount schottky diodes with a bar marked on
the cathode end, and others with a bar on the anode!

John

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