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Old 26th November 2006, 06:37 PM   #1
ash_dac is offline ash_dac  United Kingdom
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Default Power supply rail sag


As a power amplifier power supply rail "sag's" I assume it makes it more likely that clipping occurs.

Are there any rail sag effects on distortion generally before the clipping point is reached?

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Old 26th November 2006, 08:07 PM   #2
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The supply rail droop is approximately:

E = I * t / C

you usually think of t as some period shorter than a half-cycle since the diode does not conduct the entire time.
Why, silly hare, are you fleeing from the fierce jaws of the lion now grown tame?
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Old 26th November 2006, 08:36 PM   #3
Duo is offline Duo  Canada
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Depending on the design and operating conditions of the amplifier circuit, power supply droop could cause anything from detestable to immeasurable effects on distortion.

Something with really good power supply rejection should have no troubles here.

Something like a resistively loaded class A stage on the other hand could show drastic changes in characteristics with a power supply voltage change (thus why big caps or good regulators are needed).

I have some topologies for large power output (1000W+) that operate without any noticeable effect down to +/-1.5V which goes to show that a normal power supply droop will cause no need for concern.

You just have to look at how your specific amplifier deals with this.
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