1N4148 - Anything better?

[MaxHeadRoom78]

I usually use an external high speed rect in parallel with the internal one, source to drain.
Also http://www.irf.com/technical-info/appnotes/an-936.pdf
Max.

 

[Tony Stewart]

Dont think that works unless it is a zener. The app note shows how the Zener clamps the +ve spike on low side driver.

I usually use an external high speed rect in parallel with the internal one, source to drain.
Also http://www.irf.com/technical-info/appnotes/an-936.pdf
Max.

 

[maicael]

1. No, unless it is push pull.. the diode goes across the inductive load in reverse of normal direction, rated for same current and forms a smaller current loop.
2. No, unless just used at low rates as all diodes have capacitance.

Depending on speed diode must be a fast recovery type Schottky. The normal Body diode unless a zener does not protect for overvoltage because the diode is in reverse connected to Drain instead of V+ for low side switch.

Ok. Thanks
But for question 1, you said no "unless its push pull..."
So how do I place the diode in push pull cos I do push pull application for people?.
And I play around sometimes
Also it has to be a zener right or will an ordinary diode do in this configuration..

 

[Tony Stewart]

Ok. Thanks
But for question 1, you said no "unless its push pull..."
So how do I place the diode in push pull cos I do push pull application for people?.
And I play around sometimes
Also it has to be a zener right or will an ordinary diode do in this configuration..

Push-pull means complementary or half bridge driver.

 

[MaxHeadRoom78]

I use mine on a full bridge.
Max.

 

[Tony Stewart]

I use mine on a full bridge.
Max.

Then you would still need a zener if bipolar or diode across coil to V+ , if unipolar for fast low side turn-off +ve transients.. Right?

 

[MaxHeadRoom78]

I use a hi speed Schottky as example here **broken link removed**
The internal diode is traditionally fairly small and not that fast.
Max.

 

[maicael]

Push-pull means complementary or half bridge driver.

Yes I know but what I was asking was how do I place diode for MOSFET protection in push-pull application.
Have seen a few notes though but would like to hear anyone's thoughts.