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fatcat2
modified 4 years ago

Class-H Amp

3
9
249
04:26:12
Nothing new but this works just fine. One problem though; idk why the current through the 110m ohm resistor feeding the 8 ohm load is ridiculous in shape. Idk how to calculate the THD in EC (I hope that it's moderate) and that's why idc about the effects of that "weird current". Haven't calculated the efficiency yet; will do it. The extra switch is for manually routing the wire so that it looks neater.
published 4 years ago
jason9
4 years ago
That weird current is clipping. I dunno why it clips like that, but to get rid of it simply reduce it from 37.8V to 37V. Also, a bias current of 5A is far higher than needed. It results in a constant 100W power consumption. You can reduce the 2.2kΩ bias resistor to 1kΩ to get a much more reasonable 718mA which will consume only 14W.
jason9
4 years ago
Also, for the THD, I expect it to be very small (even unrealistically so) due to the negative feedback.
jason9
4 years ago
Also, if you really want absolute minimum IRL THD you can set the bias current to 2.3A (exactly half the maximum current the amplifier outputs) which results in a constant power dissipation of 46W. I don’t know how much difference it actually makes though.
fatcat2
4 years ago
That's sort of a cross between a class-A and a class-AB, I guess. The fidelity of class-A won't be retained in that case. The distortion will be higher.
jason9
4 years ago
Yeah, that’s why I suggested a bias current of 2.3A, the minimum current at which it’s still indisputably class-A. Well, that might actually be 2.5A, but at 37V only 2.3A is needed.
jason9
4 years ago
If you really wanted maximum inefficiency (with marginal if any THD gains) you could use a 4.7A constant current source pushing current into the output wire and another transistor pulling current out of the output wire with the second one pulling anywhere between 0 and 9.4 amps.
fatcat2
4 years ago
@jason9, well, I was aiming only to reduce the THD; didn't care about the efficiency much. I chose ~5A coz the instantaneous impedance of an 8 ohm speaker can dip up to 4 ohms. In this case, the class A mode is retained even when this happens, especially with subwoofers. I could've made the current sources more efficient but I didn't care about that. I'm making a remake of this, in which I'll calculate the efficiency.
jason9
4 years ago
I see
fatcat2
4 years ago
Here's the edit:- http://everycircuit.com/circuit/6436844072599552

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