[TriEmbed] MOSFET or Relay

[Brian]

Adam's responses are good.  One more considration:  Voltage drop.  Even 
in saturation ("on"), a semiconductor will have a current-independent 
voltage drop (known as Vsd) across it that will likely be a good bit* 
larger than the drop across the relay's contacts.

To summarize:

MOSFET -
  - Fast switching (nanoseconds)
  - Very low drive current (gate current)
  - Very small "on" resistance (Rds - 10s of mOhms)
  - Fairly large "on" voltage drop (Vsd - ~1.5 V)

RELAY -
  - Slow switching (micro- to milliseconds)
  - Much larger drive current (coil current)
  - Larger "on" resistance (contact resistance - 100s of mOhms)
  - Negligible "on" voltage drop


Personally I'd rather have seen amazing strides on the Philadelphia 
Experiment!

-B

On 12/7/2015 8:41 AM, Grawburg via TriEmbed wrote:
> Just for my future information. Presuming that current draw is not an issue, given the choice between using a MOSFET or a suitably opto-isolated relay to switch 12V, is there any significant advantage of one over the other? The MOSFET seems more 'elegant', but that hardly seems like a good answer.
>
> BTW, there should be some kind of law against so many people helping guys like me. :-)  Imagine if the Manhattan Project had a group like TriEmbed.
>
>
> Thanks,
> Brian Grawburg
>
>
>
>
>
> _______________________________________________
> Triangle, NC Embedded Computing mailing list
> TriEmbed at triembed.org
> http://mail.triembed.org/mailman/listinfo/triembed_triembed.org
> TriEmbed web site: http://TriEmbed.org
>