schottky diode

[shermaine]

may i know the advantage of using schottky diode as discrete device and situation where i can use schottky diode as discrete device?

 

[audioguru]

The forward voltage of a schottky diode is much less than a silicon junction diode.

 

[Papabravo]

I believe the reverse recovery time is also smaller. This is important in applications where it is necessary to limit the magnitude and the time of the reverse current flow.

 

[Sceadwian]

According to Wikipedia reverse recovery for a fast PN diode is on the order of 100 nano seconds. Reverse recovery for a fast Schottky diode is on the order of 100 pico seconds. That's more than a couple orders of magnitude faster. Higher power Schottky's have a reverse recovery closer to 10 nano seconds.

 

[dknguyen]

Schottky has lower forward voltage drop when conducting and can turn on/off faster. However, it has higher reverse leakage when not conducting and does not come in as high voltage ratings.

So you can use schottky diodes to provide a path for inductive flyback currents, but probably cannot use them for polarity protection

 

[Hero999]

It depends on how susceptable your device is to reverse polatiry, if it'll take reverse polarity as long as the current is limited then a schottky will do. If you're worried about the small leakage ruining your sensitive device then simply connect another diode in reverse parallel with it.

 

[mneary]

If you're worried about the small leakage ruining your sensitive device then simply connect another diode in reverse parallel with it.

Please give an example.

 

[dknguyen]

Please give an example.

I don't quite understand either.

 

[Hero999]

I mean in reverse parallel with the device.

 

[Nigel Goodwin]

I mean in reverse parallel with the device.

Surely that's in series?, not parallel - which is why everyone is confused?.

 

[Gayan Soyza]

I remember what I learned from my course.

Applications

*Used in audio frequency applications because of its high switching speed and high frequency capability.

*Their high current density and low forward voltage drop improves less power wasted than if ordinary PN junction diodes

*They were used in the 74LS (low power Schottky) and 74S (Schottky) families logic circuits. The diode is inserted between the collector and base of the driver transistor to act as a clamp. Resulting BASE COLLECTOR junction FORWARD biased so the turn off time of the transistor will be reduced bcuz the transistor is driven HARD ON & helping to improve the speed of the circuit.

What else?

 

[ericgibbs]

I mean in reverse parallel with the device.

To add to the confusion!

I think he means D2 in reverse parallel with RL, so that RL dosn't see a negative voltage due to leakage thru D1....

I cant see that happening as the source Voltage is always positive on the drawing, but if the Vsource was a +/-V... perhaps.

 

[Hero999]

To add to the confusion!

I think he means D2 in reverse parallel with RL, so that RL dosn't see a negative voltage due to leakage thru D1....

Yes, that's what I meant.

I cant see that happening as the source Voltage is always positive on the drawing, but if the Vsource was a +/-V... perhaps.

It's just an illustration, if you reversed the battery polarity the D2 will conduct the reverse leakage current through D1 so it won't damage the device.

I don't see why everyone's confused, the diagram should be fairly self explanatory.

 

[ericgibbs]

hi,
Thanks for the clarification