Just Curious

[iRavenoak]

I am an electro-tech student and I was wondering what would happen if I used a diode that was too big. The tv I am working on requires a diode (in5406) and I only have (in5404) and (in5408) at my disposal.

 

[Nigel Goodwin]

I am an electro-tech student and I was wondering what would happen if I used a diode that was too big. The tv I am working on requires a diode (in5406) and I only have (in5404) and (in5408) at my disposal.

As long as it's a higher spec, then it's perfectly fine - however, I would suggest a 5404 is a LOWER spec (actually lower voltage) than a 5406 - personally and professionally I only stock the 1N5408 for replacing any in that range, there's no point keeping poorer ones.

 

[ericgibbs]

hi,
I would use the 1N5408, its got a higher reverse voltage rating, but that will not be a problem
E

 

[AnalogKid]

In your application, the 5408 higher voltage rating has no consequences. Generally speaking, as the voltage rating of a diode increases, so does its forward voltage drop (Vf) at any particular current compared to other diodes in the same series with lower voltage ratings. This almost never is a problem, but can affect efficiency if you are sweating every milliwatt.

ak

 

[Pommie]

In your application, the 5408 higher voltage rating has no consequences. Generally speaking, as the voltage rating of a diode increases, so does its forward voltage drop (Vf) at any particular current compared to other diodes in the same series with lower voltage ratings. This almost never is a problem, but can affect efficiency if you are sweating every milliwatt.

I have never heard this before. I just checked the datasheet and the full range of 1n540# diodes have a forward voltage of 1.2V. Where did you hear this?

Mike.

 

[pfofit]

Have a look at the datasheet for uf400X, for an extreme case.

 

[dr pepper]

Poms, its the reverse voltage they were talking about, that is how much voltage the diode can withstand when its off.
Forward voltage (0.6v) is not often considered except for high power applications such as switching supplies where schottky diodes are often used which have a forward voltage of 0.4v or thereabouts.

 

[Pommie]

Poms, its the reverse voltage they were talking about, that is how much voltage the diode can withstand when its off.
Forward voltage (0.6v) is not often considered except for high power applications such as switching supplies where schottky diodes are often used which have a forward voltage of 0.4v or thereabouts.

You need to reread the above posts.

Mike.

 

[chemelec]

Use the 5408 Diode.
Having a HIGHER Rated Voltage Diode is Always Preferred To one that is Under Rated in Voltage or Amperage.

Doing a Test on a 1N5400, 1N5406 and a 1N5408, ALL Three Basically Measured the Same Forward Voltage Drop. Give or Take 0.1 Volt.

 

[dr pepper]

Did I get that completely wrong, sorry Mike.