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Posts by wakibaki

  Absolutely not. It will make the crosstalk worse.   w
You can build a CMoy with an AD8397 as a direct substitute for whichever opamp. You will need to etch a board, however, to take advantage of the high current/power of which it is capable. It needs the pad on the bottom soldered to a large area of copper on the PCB to act as a heatsink. The easiest way to do that is to use SMT components on the top side, leave the bottom surface unetched and drill a fair-sized hole that will allow you to fill it with solder and make a...
AMB's Mini3 uses an AD8397 in one of it's variations.   The AD8397 has the virtue of swinging ~rail-rail. It has no short-circuit tolerance, however.   w
I had one of the opamps upside down in the original drawing...     You should be able to see (I think), if you expand the picture, that the legend in the bottom left hand of the screen shows 498.301nA. This is the current in the ballast resistor. The offset voltage (from midpoint) is ~4mV. This takes no account of opamp input offset voltage, however, but the error due to variation in regulator voltage references and consequent quiescent current is likely to be...
A simple (not so simple) way round this is to use a single regulator and make sure that it is on the correct side to pass any DC bias in the returned current from the amplifier. Unless you want to match each regulator to each amplifier this presents its own problems.   You might find that with a suitable opamp, the opamp/transistor circuit I drew can actually be built to reliably outperform the regulator circuit in terms of wasted power. It can certainly be built to...
Good question Kim, I should have paid more attention.   We're not dealing with DC here, we're dealing with AC. As long as the the net current is zero there will be no problem, there are some big caps there. What I should have thought of, and which is why he is getting the result he does, is what happens at DC. If there is a net DC bias that exceeds the leakage through the caps and the adj. pin there could be a problem.    Sorry goldpoint, your point is well...
  No I don't see. It doesn't sound at all likely to me. You obviously did not monitor the ground-to-opposite rail voltages when you did the tests. If the ground point moves toward the positive rail, the negative rail must move toward the positive rail by double the amount, because the 2 resistors and the zener diode keep the regulator adj. pin at 1.25V negative of the centre point, and its output therefore at the centre point.   As Kim said, the 2 outputs should be at the...
I think that with just 1 regulator the sinking impedance and the sourcing impedance may not be symmetrical. This would have to be tested, at least in simulation. The advantage is that there are no problems with matching and no necessity for the ballast resistors with a consequent lower output impedance and no possibility of power being wasted if the two regulators end up producing slightly different voltages.   It just illustrates IMO, the reasons to stay away from...
  There is only one ground. How can half of it be regulated?
Looks good to me Kim, but maybe some of it is unnecessary...       w
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