IXYS GaAs Schottky Diodes.

[Tweeker]

Has anyone tried these IXYS 600V several amp Gallium Arsenide Schottky Diodes?

If you've tried any GaAs diodes, how did they do and where did you get them?

The IXYS DGSS 6-06CC is a 3 pin TO-220 chip, 2 300V diodes in series with pin 2 between the two diodes. For the 2 on the chip, the diodes are rated to be used in series. Ultra low junction capacitance of 4 pF. 11amp @ 25C, 6amp @ 90C.

[tubelab.com]

It seems that it takes a few months for IXYS parts to go from the web site to the distributors shelf. I waited for 4 months to get the 10M45 chip when it first came out. They have had the 900 volt version on their wep page for 3 months. The only distributors that stock them have large minimum order requirements. Their web page also lists some cool high voltage mosfets, but nobody has any in stock. Most IXYS parts wind up at DigiKey eventually.

[andrei]

600V reverse voltage rating is a bit low for most vacuum tube circuitry. Designing for 15% safety margin, you get 250VDC peak out of full-wave rectifier. After the ripple filter, you are looking at 200VDC, maybe. Enough for low voltage tubes in a preamp, or maybe 6AS7... Cree makes interesting 1200V SiC rectifiers, but they are sort of expensive.

[Tweeker]

Why would you use other than a bridge with SS diodes? I'm not trying to adapt a design to old power transformers. Is there something Im missing here about tube operation?

[Bandersnatch]

Hey-Hey!!!,
The full bridge doesn't have to be made with four SS diodes either. Currently running a hybrid bridge. Two 600V General Instruments fast/soft and a GZ34 in parallel for the for the forward facing diodes.

Soft start for L-C filters leaves a bit more safety margin for SS diodes...
cheers,
Douglas

[tubelab.com]

For a full wave CT configuration (the common circuit used in tube amplifiers) the rectifiers must be capable of withstanding 2.82 times the maximum voltage (1/2 of the secondary) that the transformer puts out. This usually happens at initial turn on before the tubes get hot.

A full wave bridge requires rectifiers capable of 1.414 times the secondary voltage.

If a new transformer is being used the choice of configuration is a matter of personal preference. Often there are more transformers available for the full wave CT configuration.

For new designs it is often cheaper to use a toroidal transformer that was made for non tube applications. It seems that the price goes up if the word "tube" is in the description. My 300Beast amplifier uses a Plitron 300VA toroid (2 X 175 volt windings in series). This transformer delivers about 370 volts with a choke input filter and about 450 with a cap input filter. I use Hex Fred diodes in this amp. I have some shiney new 600 volt silicon carbide schottky diodes to try in it, but haven't found the time yet.

DigiKey SDT04S60IN.