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Originally Posted by nikongod /img/forum/go_quote.gif
You are showing LOAD current in both examples, and IMO mistaking it with idle current.
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No, I'm not.
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The amplifier in example B will behave VERY differently depending on whether it is in class-A or class-B. |
They both behave the same in that all of the currents flow through ground.
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This disagrees with your first quoted statement by showing a clear difference running the amplifier in example B class-A or class-B |
The only difference in example B in class A versus class B is that in class A, the current will be constant, whereas in class B the current will be variable.
This has absolutely nothing to do with the primary point that
all of the current flows through ground. That contrary to claims made, ground is
not bypassed by using an "active ground" channel.
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You say right here that the load currents sum to zero in the active stages of example B running class-A, how can they then get to ground if they have summed to zero? |
You're misunderstanding what "summed to zero" means.
All currents in a given node "sum to zero" (see Kirchhoff's Law). But that doesn't mean that there is NO CURRENT through the node. What it means is that the current entering the node must be equal to the current flowing out of the node.
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Its good to know you agree with AMB that the load current dosnt go to ground. Arent we talking about the load current here? |
I don't agree with AMB that load current doesn't go to ground. Because it does go to ground.
Once again, it doesn't just spill out onto the floor or evaporate into the air.
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in this quoted section you again mention a BENEFIT to running the amplifier in example B in class-A due to the constant load that it represents to the power supply. this contradicts the first quoted bit AND you maintain elsewhere that these topologies are without merit or benefit! come now. pick one. |
I'd previously acknowledged a number of times throughout this thread that keeping power supply current draw constant could be of some benefit.
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all of the current goes through the PS, but none of the SIGNAL CURRENT goes to the power supply in the amplifier in example B running class-A. it is not difficult to see a long list of advantages from this. |
ALL of the current goes to the power supply.
Again, it's a matter of whether or not the current is constant, or variable.
But that doesn't change the fact that the claims made that an "active ground" bypasses ground are erroneous. And that's the issue that the illustrations were intended to illustrate.
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I prefer the simplified schematic although it is a strawman because it illustrates the faults of a class-B amplifier where class-A amplifier works realllllly well. |
It's not simply a matter of class A. A class A amplifier does not inherently draw a constant current. A simple class A amplifier with a complimentary push pull output stage will draw varying current from the power supply depending on the signal. To get a constant current, you need to bridge it with another class A amplifier with a complimentary push pull output stage.
And that's really all an amplifier with an "active ground" is, is a pair of bridged amplifiers. The only difference is that one of the amplifier channels isn't driven with a signal.
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