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TPA2038D1: THD+N test condition

Part Number: TPA2038D1

 

Hello

My Customer had tested TPA2038D1EVM, but  they says THD+N is bad ( 0.4%).

I told him the reason why may be due to output filter.

They intend to use TPA2038D1 for FY18 conference sysytem.

Q1

Is this idea correct?  

 

where: TPA2038D1 EVM

Output filter is FB1, FB2( Ferrite Bead). http://www.tij.co.jp/jp/lit/ug/slou298/slou298.pdf

TPA2038D1 data sheet page8 Fig13: 8ohm + 33uH Gain=6dB

 

Q2

In data sheet Fig13,  condition is L=33uH, but what is the C value for LC filter?

<Back Ground>

EVM Test Result by customer Po=50mW, THD+N Ratio=0.41%

Po=50mW  THD+N Ratio=0.04%(Datasheet P8-Fig.13)   <Customer's Test Setup>

/TPA2038D1YFFEVM Rev D Vdd=+5.0V, RL=8Ω, Gain=+6dB

/Audio Precision SYS2722 internal 20~20KHz filter used

/AP(Out,1kHz Sine Wave) ⇒EVM⇒ 30kHz LPF(RC) * ⇒ AP(In)

* customer reffered

http://www.tij.co.jp/jp/lit/an/sloa068/sloa068.pdf

 

  • Hello Shibatani-san,

    The device's measurements were performed as it is shown in the Test Setup for Graphs section of the amplifier's datasheet.
    Did they use a 30 kHz output low-pass filter to make the measurements? could you provide the customer measurement circuit?

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer
  • Dear Luis san,

    Thank you for your reply immediately!

    Here I attached customer's test setup as attached (ppt).

    They don't use 33uH , but Ferreite bead  (default as TPA2083D1 EVM).

    Would you please there is anything wrong ?

    Also  please advise  detail test-setting ( LC filter ) in TPA2038D1 data sheet page8 Fig 13.

     

    Thank you and with My best regards

     

    TPA2038_THD+N_setup.pptx

     

     

     

  • Shibatani-san,

    Everything in the circuit seems to be right. The inductor of 33uF is added to the load to simulate a speaker, this inductor isn't referring to output filter.
    The amplifier output signal can get distortion if the THD+N is higher than 10%, but this is not the case, Why does the customer say THD+N is bad?

    Best Regards
    José Luis Figueroa
    Audio Applications Engineer