Do some research on NMOS or PMOS designs from the 70's.

We guessed!
The constant current load circuit you have will be about 25% efficient.
You can get to about 50% and remain in class A by using semiconductor versions of White cathode follower and SRPP valve circuits.
You can get to 78% using class B (just a bit less for class AB, which is Siliconix Autobias etc.)
Class D will take you into the >90% region.

I remember taking a lecture course on amorphous silicon back in my 3rd year at university back in 1986 - I remember it being scheduled for 9am on Saturdays.
What I don't remember from it (maybe due to what I was doing on Friday nights) is whether the FETs were enhancement or depletion or whether you could make both, and whether you could construct P-channel devices.

Ahahah Friday nights ahahah been there done that ahah.
Due to the nature of the IGZO transistors I think I can't make depletion ones. :s

 

What do you mean by “ one type of technology”?

Sorry for lack of better terminology, but what I meant was trying to use only IGZO transistors.

 

Ahahah Friday nights ahahah been there done that ahah.
Due to the nature of the IGZO transistors I think I can't make depletion ones.

I found this in 5 minutes.

 

1985 Siliconix Autobias Amplifier is all N-channel
http://www.bitsavers.org/components/siliconix/_dataBooks/1985_Siliconix_MOSPOWER_Applications.pdf
Starts on page 348

Click "go to page" and enter "348". Or if you are using an iPad slide the "page number" slider until it gets to 348.

 

I found this in 5 minutes.

View attachment 245098
View attachment 245099

Well this just made my day ahah Thanks you very much!!!

 

Well this just made my day ahah Thanks you very much!!!

If you can make depletion-mode devices, then look at all the possible valve circuits - everything is N-channel because you can't make P-channel valves!
http://www.valvewizard.co.uk/SRPP_Blencowe.pdf
https://www.tubecad.com/2019/04/blog0462.htm
In both cases, the circuit can be made with depletion FETs, but it is probably more efficient if the upper device is depletion and the lower device is enhancement.

 

If you can make depletion-mode devices, then look at all the possible valve circuits - everything is N-channel because you can't make P-channel valves!
http://www.valvewizard.co.uk/SRPP_Blencowe.pdf
https://www.tubecad.com/2019/04/blog0462.htm
In both cases, the circuit can be made with depletion FETs, but it is probably more efficient if the upper device is depletion and the lower device is enhancement.

Sure!! I'll check everything you guys send me here. You have already been more helpful than my advisor.

 

Sure!! I'll check everything you guys send me here. You have already been more helpful than my advisor.

If Theo Williamson could manage 0.1% THD @ 25W back in 1947 with only N-channel devices, I'm sure you can!

 

If Theo Williamson could manage 0.1% THD @ 25W back in 1947 with only N-channel devices, I'm sure you can!

I've never heard of him but It is also good info to give more context and prepare a better story

 

I've never heard of him but It is also good info to give more context and prepare a better story

https://en.wikipedia.org/wiki/Williamson_amplifier
Learned electronics whilst recuperating from tuberculosis, mainly into industrial automation and was made a fellow of the Royal Society for designing machines to make cigarettes more efficiently. The irony of it. . . . . .

 

As a circuit designer should I be worried about process variability in transistor characteristic curves in order to develop the circuit? I mean, I would like to see this work but from my initial lab data I can see a lot of variation in Vt values and ION currents.

 

I design circuits so that they work perfectly with devices that have minimum, typical or maximum specs.

 

I design circuits so that they work perfectly with devices that have minimum, typical or maximum specs.

Agreed - but it's taken me many years to design an audio power amplifier design that doesn't need a bias adjust preset (and my circuit only works with complementary output stages)
If you've only got N-channel, then there's the Siliconix "autobias" that was mentioned previously, but it's not exactly in the -100dB distortion category.

 

Agreed - but it's taken me many years to design an audio power amplifier design that doesn't need a bias adjust preset (and my circuit only works with complementary output stages)
If you've only got N-channel, then there's the Siliconix "autobias" that was mentioned previously, but it's not exactly in the -100dB distortion category.

Thank you once again for taking the time to help me