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It is currently 17 Jun 2019, 18:44

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 Post subject: Class D with Ga N fets?
PostPosted: 23 Apr 2019, 01:45 
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Joined: 13 Jan 2018, 21:33
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Location: australia
I saw this article on the sister site. Maybe of interest. could these devices improve all amplifier classes?https://www.psemi.com/pdf/app_notes/an72.pdf

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PostPosted: 23 Apr 2019, 07:06 
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Joined: 06 Apr 2009, 10:08
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Woodo wrote:
Could these devices improve all amplifier classes?
Unlikely.

Using GaN devices in class-D audio amplifiers could lead to increased efficiency but gains achieved will be marginal as efficiencies are already 85%+. In linear amplifiers, the advantages are only to be found in power output vs package size and thermal design. GaN devices are mostly applied to high power RF amplifiers to increase efficiency.

A point to remember, "Application Notes" as published by the semiconductor manufacturers are more marketing material than technical support.

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PostPosted: 23 Apr 2019, 16:20 
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Thanks Matt, traps for the unwary. I guess whatever gains in sound quality - objective and subjective - from these improvements will be incremental.

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PostPosted: 23 Apr 2019, 16:49 
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Don't get me wrong. I'm an RF guy and I love GaN. As a high power semiconductor it is allowing us to do things in RF power and packaging design we could only dream of previously. It's just not a universal solution.

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PostPosted: 24 May 2019, 05:55 
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Gan fets are used in switcihng power supplies, you can see some refrence desings on ti that uses these.
Class D is basically a switching power supply but instead of a voltage refrence, you feed the feedback system a audio signal and you get a power amp.
Theres a youtube video of a lecture which explains briefly class d.

I didn't learn detail of gan fets, but one of the main features are very low capacitance so you can have higher operating freqency.
Ti refences only uses gan when extremly high switching frequncy is desired in the design

As most class d amps don't even operate on super high frequencies all that needed is transitors of fair capacitance and you want the linear hifi one.
Low capacitance dosen't always mean hifi sound.
The class d amps if operate v high freq then the gain stages and feedback system will not work well, high gain bandwith is hard to achive so the distortion increases if you over do the frequency switcyhing


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