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Criteria for choosing 'silicon' or Schottky diode

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sjb741

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The criteria I currently use are
  • Schottky diodes tend to have greater reverse leakage (and the lower the Vf, the larger the leakage)
  • Schottky diodes have less forward voltage drop (Vf)
  • Schottky diodes have zero stored charge
From the above list, I'd only prefer a silicon diode if leakage current is an issue.

I'm wondering though whether there are other things to consider - either in terms of usage/application or in terms of other contrasting characteristics not listed above?
 

Expect 100V or less reverse voltage rating for "normal" Schottky diodes.
Most are 50V or less.
 

Many thanks, I never thought of that, and it would have mattered in my application.
 

Hi,

I prefer to
* first decide the requirements of the application (usually there are application note telling what part parameters to care for)
* then do the parts (diode) search with the decided prameters. Usually using the parametric search tools provided by distributors and semiconductor manufacturers

Klaus
 

RF Applications as mixers.

Good list here of application space -



Regards, Dana.
 

For power consider the high-current Vf if you can find a spec. Schottkies do not have the conductivity modulation of a PN silicon diode so Vf vs If runs up a lot more with current.

Schottkies above maybe 60V get P guardrings to control edge breakdown. That places a PN diode in parallel.

Now this feature can raise recovery time, big time if you push Vf over 0.7V (and harder as you go). If you care about storage / recovery time be real careful about any such hints you may find. Like, do you want recovery time to blow out from 10nS (a sandbagged spec for something supposed to have zero, to cover test) to 2uS at high or overrange load, maybe to blow out an opposing power switch during now-shoot-through?
 
True power schottkies only go to 45V - above this they are a compromise silicon diode with a guard ring - with higher Vf than for true schottkies.

True schottkies have high capacitance - which leads to over volt spikes for fast power circuits ( due to wiring inductance ) - so they need protecting with snubbers or diode/zener voltage limiters - if you go over ~ 50V on a 45V schottky - bang ..!

even a very narrow spike will achieve destruction.

The leakage currents can be well over 1mA at 100 deg C
 
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