Here a pic of an idea I just have and try...5 watts RMS, but at 3Mhz switching frequency, open loop, with booth fet ground referenced...Drain signal is a bit poor, but sound quality seem incredible!
fredos
www.d-amp.com
fredos
www.d-amp.com
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Hi Fred,
Where's the discovery in this? 3Mhz open loop good?
Did you get the subject field cleared by the powers that be ... font's not too big or anything? It's kind of in a grey area after all.
If I had a pro audio site/business, I wouldn't be posting a schematic like that, and with that title, and certainly not to make a point
Where's the discovery in this? 3Mhz open loop good?
Did you get the subject field cleared by the powers that be ... font's not too big or anything? It's kind of in a grey area after all.
If I had a pro audio site/business, I wouldn't be posting a schematic like that, and with that title, and certainly not to make a point
Just the idea to put 2 flyback convert out of phase to be able to drive mosfet on common source. It's exactly the same principle of dual forward DC converter, when one push, the other pull on freewheling...Nobody have seen that??? Drain voltage go over twice the supply with some garbage, but dont seem to affect sine wave..And dead time between 2 switch dont seem to have effect too... I can push it to 3 mhz before to feel the output get warm. Sorry if I dissapoint you guy, but that was an idea and I have try it. Dont know if I can got ''bigger result'', but idea work on breadboard with cheap components...And work on first try without any calcul...I use a LM361 to drive the CMOS and first drivers with a 5-12V level shifter...Really simple!
Take a better look at schematics, I have do it just for you!
Fredos
Take a better look at schematics, I have do it just for you!
Fredos
A 3 Mhz switching frequency imposes a 333ns period, which means that every half cycle lasts for 166ns when the amplifier is idle. In order to achieve class D operation, each MOSFET must be fully turned on and then fully turned off within that 166ns period, and each switching event should last for a very small time in comparison with the main switching period.
Now, how much do you think that a IRF640 takes to turn on and turn off with a 10 ohm gate resistor and considering the high and non-linear typical MOSFET output capacitance in the Vds<25V range?
What a nice linear amplifier you have built, indeed (the filtering is done at MOSFET gates). Next time take the dust out of one of your oscilloscopes (assuming you own one capable of showing a 3Mhz square wave without too much "edge rounding"
) and use it to check if your stuff really works as expected (including your commercial amps 
)
A circuit producing some sound, even at high powers, does not neccessarily have to be working properly or as expected.
BTW: And yes, you have discovered linear amplification
Now, how much do you think that a IRF640 takes to turn on and turn off with a 10 ohm gate resistor and considering the high and non-linear typical MOSFET output capacitance in the Vds<25V range?
What a nice linear amplifier you have built, indeed (the filtering is done at MOSFET gates). Next time take the dust out of one of your oscilloscopes (assuming you own one capable of showing a 3Mhz square wave without too much "edge rounding"
) and use it to check if your stuff really works as expected (including your commercial amps )A circuit producing some sound, even at high powers, does not neccessarily have to be working properly or as expected.
BTW: And yes, you have discovered linear amplification
Hi Fredos,
I'm afraid you only get an output signal thanks to the imperfections of the real components:
The average voltage at the drains of both FETs must be 0; the waveform might be widely assymetrical, but it doesn't matter: the volt-second product across a perfect inductor has to be 0 over a period of time, otherwise the current will climb indefinetely.
Your inductors have some series resistance, which allow some AF signal to leak through; with better inductors you'd get nothing.
LV
I'm afraid you only get an output signal thanks to the imperfections of the real components:
The average voltage at the drains of both FETs must be 0; the waveform might be widely assymetrical, but it doesn't matter: the volt-second product across a perfect inductor has to be 0 over a period of time, otherwise the current will climb indefinetely.
Your inductors have some series resistance, which allow some AF signal to leak through; with better inductors you'd get nothing.
LV
Drive it with LM361, but like I told, square was like a sine wave a these frequency, and resolution go out rapidly. I just told that I push it to 3 mhz before output get warm! Optimal setting was near 700Khz and under. Have try to close loop, but don't able to make it stable...Anyways, was just the try of an idea...And sorry for all others that think this is a linear converter or space communication device...
Fredos
Fredos
This circuit is flawed from a theoretical perspective: it simply cannot work. L1 and L2 should be made large enough to present a high impedance in the audio band; it would then become a "double single-ended class A/D amplifier". A real mess, yet it could work; but with proper 47µH's, no way: the outputs have to stay at a 12V average. Any output voltage is caused by the parasitic series impedance of the coils. You cannot rely solely on parasitics to make a circuit work.
LV
LV
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