Ixys depleationmode fet susy one stage balanced pushpull Zenitronamp. - diyAudio
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Old 27th November 2009, 06:14 PM   #1
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Default Ixys depleationmode fet susy one stage balanced pushpull Zenitronamp.

Click the image to open in full size.'

I just posted about this amp in another thread but i wanted to open a new thread about this amp.7
I read about Ixys having a high power depleationmode fet, and i got realy intressted. Thiis is what i would like to build.
I can not imagine a better topology for a ultrasimple amp.

Its a supersymmetric fully balanced one stage pushpull amp. Quite a mouthfull to say!
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Old 28th November 2009, 09:16 AM   #2
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That looks like a really interesting design. I like it. To be honest I'm having a little trouble following this. Are you saying it's a super symmetric Circlotron?

Okay, I see the two circles, and the susy feedback. Looks like the 33 ohm resistors set the bias current? I'd love to see this built. Good luck!
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Old 28th November 2009, 11:56 AM   #3
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Default Iwas going to write more about it yesterday...

Quote:
Okay, I see the two circles, and the susy feedback. Looks like the 33 ohm resistors set the bias current?
Its a supersymetric circlotron amp. The two 33 ohm resistors just make a groundreference point. Nothing else.
Bias is set by the depletionmode-fets and the DC-resistans of the big inductor.

The bifilare inductor does two things. It isolates the Sources from the drains on the Fets so they can provide voltage-gain, and it provides a I/V converting - like a constant currentsource or a powerresistor does in an normal Zenamp.

Here is a simplified version, with power-resistors instead of inductors.
I have left out bias-arrangement for clearity.

Click the image to open in full size.
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Old 28th November 2009, 11:58 AM   #4
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The connection between the sources of the Fets is the same thing as in a LTP. Its basicly a circlotron-LTP (Long Tailed Pair).
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Old 28th November 2009, 12:05 PM   #5
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I have been building different Circlotons since 2001, and i came to think of this one when i read Nelson Pass Zen V-7. Its in many ways the same amp but with floating supplies and no need for any CCS to set the currentflow though the devices.

I guess i could call it The Circlotronic Zen V-7.
A diffence from the Zen V-7 is this amp will runn in class A/B, but with a lot more distortion. I got something like 50 watts out of this circuit with 2 x 15 volts supply and 500 mA quisent current tjhrough each Fet.
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Old 28th November 2009, 12:08 PM   #6
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R1 and R2 could be powerrestors, lightbulbs, constant current sources or Nelson Pass Aleph current source.
I have drawn versions with SRPP and cascode and almost every possible variation. But i like simplicity a lot better.
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Old 29th November 2009, 11:54 PM   #7
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Default What is the DC Resistance of the Inductors?

Circlomanen

What is the DCR of the 150mH inductors?

Ejam
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Old 30th November 2009, 12:54 AM   #8
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OK, a few basic questions. What is the rated power output? Can the power be upped by increasing the voltage?
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Old 30th November 2009, 06:45 AM   #9
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Quote:
What is the DCR of the 150mH inductors?
If i remember correctly, its about 0,6 ohms. Maybe a bit high for the Ixys depletion-mode-fets.

Quote:
OK, a few basic questions. What is the rated power output? Can the power be upped by increasing the voltage?

I dont know the rated output. It can be scaled up or down as you want. With 20 volt supplies and 2 amperes of current through each fet, i can get a clean 20 watts, but it will give about 50 something watts before clipping. The distortion rises a lot when leaving class A.
With really powerful devices and a lot of heat-sink you could probably get 100 watts out of it. But I haven't tried that.
I have to buy some fets before i can build this one. I have built a similar design with IRFP250 before.

I was going to build one with normal Hexfets this past weekend, but i was to tired, so all i manged was this thread.. I hope to get some time in the near future.
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Old 30th November 2009, 07:51 AM   #10
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150mh must be a big coil?
May we have a pic?
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