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TPA3255-Q1: TPA3255 audio output frequency characteristics when 4 ohm or 8 ohm load

Anthony Yoo68
Expert 1320 points
Part Number: TPA3255-Q1

Hi~

My customer is testing the TPA3255-Q1 and has questions regarding the frequency characteristics of the audio output.


The picture below is obtained when my customer tested the output load with 4 ohm and 8 ohm at 1W output (sinewave, 200mV input).It is a frequency-specific amplification characteristic curve.


Looking at it, when 50Khz, 8 ohm load shows higher amplification characteristics than 4 ohm load, and it shows a non-flat waveform.

1. The LC filter configuration circuit at my customer's output is as below.


Is the measured waveform checked above the correct output waveform?


Why is it measured like that if it is not the correct output waveform?

2. What is the frequency band of this amp(TPA3255-Q1? Can't reach 50Khz?


My client wants to work as an amp up to 70khz.

  • 0
    TI__Mastermind 19080 points

    Hi Anthony,

    The output filter is actually a L-C-R filter. 8R speaker increased the Q factor, so you saw the peaking at cut-off frequency of the LC filter.

    To make it work with 70kHz, you need to extend your bandwidth by moving the cut-off frequency to higher frequency.

    This app note should be a good guidance for you. Thanks!

    Regards,

    Sam