About power amp distortion.

[Gaetan Mailloux]

Hi

How come some fast slew rate power amp can have a so big raise of
distortion in high frequency (5 khz and up) ?

What made a power amp to have a much higher distortion at high frequency ?
TIM distortion ? or ???

Thank you very much

Bye

Gaetan

[chung]

In general, distortion goes up as a function of frequency because the
loop gain decreases. If you look at a power amp's open-loop frequency
response, there is usually a roll-off such that the gain at 20KHz is
much less than that at 1KHz. Loop gain is the difference between
open-loop gain and closed-loop gain. Loop gain is what drives the
distortion to zero, or as low as possible, in a feedback amplifier.

The slew rate determines the power bandwidth of the amplifier. If the
slew rate is insufficient, then there will be distortion at high output
levels at high frequencies. But slew rate by itself does not guarantee
low distortion, it's just a necessary condition.

TIM is just another way of stating slew-rate induced distortion in
feedback amplifiers.

Gaetan Mailloux wrote:
> Hi
>
> How come some fast slew rate power amp can have a so big raise of
> distortion in high frequency (5 khz and up) ?
>
> What made a power amp to have a much higher distortion at high frequency ?
> TIM distortion ? or ???
>
> Thank you very much
>
> Bye
>
> Gaetan
>

[Richard D Pierce]

In article <6RvZa.115296$YN5.79026@sccrnsc01>,
Gaetan Mailloux > wrote:
>Hi
>
>How come some fast slew rate power amp can have a so big raise of
>distortion in high frequency (5 khz and up) ?

As a general rule, they don't. Do you have specific example in
mind?

>What made a power amp to have a much higher distortion at high frequency ?
>TIM distortion ? or ???

Generally the linearity at high levels and high frequencies is
due to high frequency limitations in teh dveices used.

But your statement that high=-slew rate amplifiers have high
distortion at high frequencies simply doesn't hold.

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