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TPA3112D1: How to improve the frequency response?

Tim Jang
Prodigy 10 points
Part Number: TPA3112D1

I'm working on Amplifier design by using TPA3112D1.

To get reference test result, I measured THD, Frequency response, S/N rate etc by using TPA3112D1EVM.

But the frequency response is going down to less than '-1dB' at over Approx. 3.4kHz.(refer to below graph)

* Test conditions

-Input voltage : DC24V

-Input audio signal: 0dBm(Unbalance)

-PLIMIT: Max

-Gain setting: 20dB(All jumpers are inserted on EVM)

-Output(Load): 8ohm resistor via matching transformer(8ohm : 8ohm)

-Measuring point: 8ohm resistor

-Test equipment : APX515(Output impedance: 600 ohm / Input impedance: 100 kilo ohm)

-dBrA: Output level at 1kHz

Is there any special method for the test?? or Is my way to measure wrong?

  • 0
    TI__Expert 6985 points
    Hello Tim! Shawn will take a look at your question and configuration. Also, have you looked at the new TPA3128 www.ti.com/.../tpa3128d2 ? It is a newer better performing amp with very similar features. Thanks, Jeff
  • 0
    TI__Mastermind 24835 points
    Hi Tim,
    The frequency response on TPA3112D1 should be flat across 0~20kHz input frequency. I believe it's a test issue, but not a device issue.
    When you use unbalance input signal, you need to set the JP5 to set EVM to single-ended mode. Could you please let me know how much is the input signal amplitude in voltage unit?
    About the output load, why do you use a transformer please? Could you please just use a 8Ohm+66uH(which is simulating the real speaker) as the load,?
    Did you check the output signal on the load by scope? Is it expected for different frequency input signal?
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    TI__Expert 6985 points
    Hi Tim! Did this work for you? Thanks, Jeff