high voltage SiC FETs-650V 1200V for amps?

[HosD18]

Hi,

I have seen several discussions about using SiC JFETs for amplifiers, however these devices only come in 650V or higher, typically 1200V, and more recently 1700V rated devices are available.

But for audio, especially DIY home audio or boutique SS guitar amps, is there a need for such high voltage?

Typical operational voltages are 400V max for 650V devices, and 800V for the 1200V devices.

I am a newbie and thinking about building an amp.

Hos

 

[gpapag]

Hi HosD18
Here is some data for these devices. They are for switching high currents and can work at much lower voltages
http://www.infineon.com/dgdl/Infineon-IJW120R100T1-DS-v02_00-en.pdf?fileId=db3a304341e0aed001420353f03a0e4b

If you are new to building amplifiers as you say, why don’t you start with designing or building an amplifier which will use semiconductors already tested and tried for audio purposes?
There are plenty of threads at the “Solid State” section, where you will find many interesting projects

George

 

[HosD18]

Hi George,

For sure this will be done in stages, but I have buckets of SiC devices and want to flush that out. It seems the HV FETs could be used as a direct tube replacement. See semisouth boiler room discussion.

 

[xrk971]

Those are lethal voltages - is it worth messing around with? Seems like the HV is great for space constrained applications or where light weight wiring is helpful.

 

[Struth]

Hi Guys

If you want to use semis to substitute for tubes, then you have to realise the difference in their voltage ratings.

A semi has an absolute voltage limit that is stated on the data sheet.

The tube also has an absolute voltage limit called the "arc over" voltage, but this is rarely listed. What is listed is a supply rating that assumes a reactive load. For example, an EL-34 is rated at 800V and can be used with an 800Va supply and transformer load. The flyback voltage in this application causes the plate voltage to peak at 1700V - almost twice the supply voltage. This is as expected for a power tube and in this case, the arc voltage is known to be 2kV for an EL-34.

So, if you use a semi with a transformer load, then the supply voltage must be less than half the voltage rating of the semi.

As stated by others, most of those high-voltage mosfets are for switching and have very low power ratings when used linearly. Typically, a 1kW+ device becomes a lowly 150W device for a DC app.

Have fun

 

[Ian Finch]

I don't think the OP is considering a HV design - just using HV JFETs as you would any of the few known audio JFET types. If he has buckets full as he says, I'm sure I would be looking to use them too.

Whether their characteristics suit audio is another matter - perhaps Nelson has looked at these already in the Pass Labs forum.