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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: Re: Since you asked... posted by Charles Hansen on July 31, 2003 at 19:54:51:
Charles,
thankyou for the answer. I have not read the AES papers so I don't know who claims what. As an aside I met Prof. Hawksford once, the name sounded like someone in tweed with, perhaps, half-frame glasses. He is nothing like that.I like the idea of as simple as possible. I plan for output source followers with class A current source pull-downs, there is no cross-over between devices so no cross-over distortion and balanced outputs will cancel any asymmetry. The diff pair is made linear by heavy degeneration to give a desired linearity for the maximum allowed input signal and the reduction in gm is offset by using large resistive loads (ie the saturated output swing is 90V pkdiff but only a maximum of 30V pkdiff). The common-mode requirements of the two stages are totally different but can be accommodated by having two independent power supplies offset so that the output common-mode of the voltage gain stage is the optimum input common-mode voltage for the follower. It is very simple, though it requires full class A and two power supplies but that's OK for a one-off DIY effort and I can easily save the equivalent of the few hundred watts of dissipation by following the family around the house and turning the lights off after them.
Because I've optimized for the output common mode (which doesn't have to be 0V as it's balanced) the input common-mode is nowhere near 0V so input ac coupling is required. Ah, but maybe a folded cascode might fix that .. I'll think on, but not for too long or this will never make it from the simulator to the workshop.Cheers,
13DoW
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- Re: Since you asked... - 13th Duke of Wymbourne 08/1/0320:42:38 08/1/03 (0)
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