Can I use an Enhancement Mode MOSFET for a source follower?

[toshiba_nz]

E.g. something like a Ganfet EPC2038?

 

[Merlinb]

You can use an enhancement MOSFET, but the EPC2038 is only rated for 100V...

 

[abraxalito]

Looks not to have very high transconductance. For signal level though probably fine, very low parasitic capacitance is a strong point.

 

[toshiba_nz]

Need to drive 834 like this (I think grid current is 30ma max)

 

[toshiba_nz]

Looks not to have very high transconductance. For signal level though probably fine, very low parasitic capacitance is a strong point.

Why is high transconductance important?

 

[Merlinb]

Why is high transconductance important?

It's not if you're comparing it to a triode cathode follower. Any MOSFET has way more gm than a triode. But the more transconductance you have, the more linear the follower becomes in the face of difficult loading.

 

[toshiba_nz]

Thanks Merlinb.

What high spec device would you recommend? (For my application)

The load will be a direct coupled MOSFET Phase Inverter C2M1000170D with Vds 970V

And I think my 834 load line is 4.44K

 

[abraxalito]

Need to drive 834 like this (I think grid current is 30ma max)

Is the X axis there volts?

 

[toshiba_nz]

Yes, volts

 

[abraxalito]

So is the GaN FET being cascoded with the SiC FET? (Just trying to figure out how a 100V Vds part is going to survive in that HT environment...).

 

[toshiba_nz]

Hello Abraxalito

The GaN Fet is configured as a source follower to drive the 834.

Just need +35V to -30V grid swing.

 

[toshiba_nz]

There are 200V GaN FETS with higher transconductance, so I kinda wondering if that tech (GaN FET) is a good option for a source follower ..

 

[toshiba_nz]

It seems mterbekke likes them as followers (post 9)

https://www.diyaudio.com/community/threads/gan-class-a-amplifier.384959/post-7228325

 

[euro21]

Do you read the Ale's blog?
https://www.bartola.co.uk/valves/2017/06/04/6sf5-driver-for-300bgm70813-se-amps/