Ultra-low forward voltage Schottky-rectifier - diyAudio
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Old 23rd July 2008, 08:22 AM   #1
h_a is offline h_a  Europe
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Default Ultra-low forward voltage Schottky-rectifier

I just found an interesting Schottky-rectifier from Vishay, the V30100S:

http://www.vishay.com/docs/88941/v30100s.pdf

Especially for power amps the extremely low forward voltage could be very handy, it's just 0.55 V for 10 A and only 0.4 V for 2 A - lower than any of these high-speed diodes.

Unfortunately reverse current is very high, at least one order of magnitude larger than other rectifiers. Junction capacitance is also very large*.

Does somebody see a drawback to this?

The price is rather low, it's tempting to use them for the power amp...

Have fun, Hannes

*could be useful for pushing resonances into harmless areas, where's the Snubber-article...
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Old 24th July 2008, 12:43 AM   #2
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look at the forward voltage.... still up around 0.85V.... not really that low of a drop. with a Vrrm of 100V, you would only go to +/-40V rails.
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Old 24th July 2008, 07:40 AM   #3
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Quote:
still up around 0.85V.
That's at 50 A!!

From my estimate such currents do not occur for say a 2 A constant load - am I wrong?

The +-40V are not a problem for me as I'm thinking more along a ClassA amp with much lower rails.

Have fun, Hannes
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Old 24th July 2008, 11:24 AM   #4
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your charging currents are higher than you think...
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Old 24th July 2008, 02:46 PM   #5
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Even in this case 0.85V is the best I've seen yet, a standard bridge comes up to 1.4V, high-speed fancy diodes about the same.

Do you know rectifiers with even less voltage drop?

Have fun, Hannes
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Old 24th July 2008, 10:02 PM   #6
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Congratulations, you have just discovered that Shottky diodes have a lower forward voltage drop than normal PN junction types
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Old 24th July 2008, 11:19 PM   #7
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A 20A schotty will also tend to have a much lower surge rating
than a standard 20A silicon diode.
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Old 25th July 2008, 12:07 AM   #8
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Quote:
Originally posted by h_a
Even in this case 0.85V is the best I've seen yet, a standard bridge comes up to 1.4V, high-speed fancy diodes about the same. Do you know rectifiers with even less voltage drop?
Scottky Power diodes have lower VF than silicon. I have seen some Power Schottky with 0.60 Volt10 Ampere. But do not remember which ones.

Schottky is always high speed, more or less. The question is if high speed is good or not so good, when delivering higher currents 50-60 Hertz AC.
To one supply that is supposed to be CLEAN DC = 0 Hertz AC.
Paralleling Schottkys would lower Voltage drop a bit further. As this halfs the current in each diode. Say using 8 diodes in a bridge. ( Normally 4 )


Ordinary Silicon Diodes can also be paralleled, to lower VF a bit.
I have never used anyhing but low cost silicon rectifier diodes.
And I am quite sure
I Never In My Life Will use anything but low cost SILICON here



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Old 25th July 2008, 02:04 AM   #9
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glass passivated silicon is what is used in most high current bridges. glass passivated devices are about 1.1V forward drop. when your rail voltages are +/- 50 V or more, a few tenths of a volt wouldn't get me to spend 2 or 3 times as much money on a bridge. there are now silicon carbide diodes out there. for now they're more expensive, and have a 2 volt drop, but are really high speed devices made for switching power supplies operating at 1 Mhz or higher. i think they can handle more current per square millimeter than silicon or schottky devices.
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Old 25th July 2008, 06:56 AM   #10
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Seems some of you are too lazy to read all posts, eh?

Quote:
glass passivated devices are about 1.1V forward drop.
The ones I can easily access have 1.4 V at 50 A...

Quote:
A 20A schotty will also tend to have a much lower surge rating
Maybe you should enjoy a look at the linked datasheet first? These are 30 A Schottkys with 250 A peak rating. Not much difference to silicon at all.

Quote:
Congratulations, you have just discovered that Shottky diodes have a lower forward voltage drop than normal PN junction types
Read the first post carefully and try again

A standard Schottky is not much lower than Silicon at same currents.

Have fun, Hannes
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