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TAS5261 THD as a function of ohmic loading

Hi,

Referencing the THD vs. output power plot on page 11 of the TAS5261 datasheet, we see that the amplifier yields considerably lower distortion into 8 ohm loads versus 6 and 4 ohms.  Can we safely assume that this relationship continues with, say, 12 or 16 ohm loads?  Could TI supply any plots showing the THD + noise into 12 or 16 ohms?

Thanks!

  • Hi, JD,

    That is safe to assume. I'm sure there's some point where it asymptotically approaches a limit, but, generally speaking, yes, THD will improve with higher load impedances.

    I looked around, and I couldn't find any THD data for 12 or 16 ohms. What kind of load are you planning on driving?

    -d2

  • Thanks for the response Don.

    I asked because I'm driving an array of transducers that could be configured to yield a variety of different ohmic load values.  I figured there was an inverse relationship between THD and the load impedance because that's generally the case with all amplifiers, but I'd like to select the load value that produces the best possible THD curve.  In referencing that plot I mentioned from the datasheet, we can say that 8 ohms is better than 6 and 4 ohms, but it isn't exactly intuitive how it is better.  That is, if I didn't have the plot in front of me to look at, I would have guessed that it was better at 8 ohms, but I wouldn't have guessed at the exact shape of the curve.  That's why I wanted to see a plot if possible that shows the performance at 12 and 16 ohms.  It might seem like splitting hairs, but I'd prefer to select the optimal configuration at the outset of the design, given that I have the flexibility of doing so.

  • JD,

    We have an EVM available for this device -- I just noticed it is a little difficult to find on our website. Here is the URL:

    http://focus.ti.com/docs/toolsw/folders/print/tas5518-5261k2evm.html 

    You could get one of these and then use it to optimize your design.

    -d2