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help understanding diagram (class D amplifier)
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moretti12:
Hello guys.
I have this diagram of a class D amplifier that im trying to understand and i stumbled across this "DC stabilizer".
Obviously the first op-amp creates a triangular curve. But what's the purpose of "DC stabilizer" and how does it work? To me it looks like another integrator with feedback to the first one.
Zero999:

--- Quote from: moretti12 on November 17, 2018, 08:00:26 pm ---Hello guys.
I have this diagram of a class D amplifier that im trying to understand and i stumbled across this "DC stabilizer".
Obviously the first op-amp creates a triangular curve. But what's the purpose of "DC stabilizer" and how does it work? To me it looks like another integrator with feedback to the first one.


--- End quote ---
The embedded link to the schematic is broken. Please upload it here as an attachment. Another issue is I often check this forum using my work's computer when on my coffee/lunch break or after hours and the firewall blocks many other sites.
moretti12:
corrected :)
jmelson:

--- Quote from: moretti12 on November 17, 2018, 08:00:26 pm ---Hello guys.
I have this diagram of a class D amplifier that im trying to understand and i stumbled across this "DC stabilizer".
Obviously the first op-amp creates a triangular curve. But what's the purpose of "DC stabilizer" and how does it work? To me it looks like another integrator with feedback to the first one.

--- End quote ---
It is to keep the triangle wave perfectly centered around zero.  This keeps DC out of the load, which would be a problem if feeding a loudspeaker, for instance.  I used a very similar circuit in a class-D servo amplifier I built.

Jon
schmitt trigger:
Many times, opamps with excellent AC performance, may not have the best DC performance. In a DC-coupled amplifier, a DC performance parameter of particular interest is DC offset, for the reasons outlined above.

Therefore, you incorporate an opamp with outstanding DC performance in the feedback loop, and you get the best of both worlds.

Nowadays, there may be modern amplifiers with both outstanding DC and AC performance, but I suspect that they are either too expensive or single sourced. Or both.

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