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OPA1688: load issue

switch
Genius 4120 points

Part Number: OPA1688
Other Parts Discussed in Thread: OPA1622,

Tool/software:

Hi ti team，

When the OPA1622 operates at a volume level of -4dB with no load:

  • The OPA1688 has an input voltage of 1.173 V and a THD+N (Total Harmonic Distortion + Noise) of 0.042777%.
  • The output of the OPA1688 is 1.519 V with a THD+N of 0.061113%.

However, after connecting a 24Ω load:

  • The voltage at the pre-stage of the power amplifier is 1.173 V with a THD+N of 0.039162%.
  • The output of the OPA1688 is 866.9mV with a THD+N of 28.15%.

As shown in the figure below: Please help analyze what causes this?

  • 0
    TI__Guru* 77501 points

    Hi Switch,

    switch said:
    The output of the OPA1688 is 866.9mV with a THD+N of 28.15%.

    The OPA1688 is not designed to source or sink heavy load (e.g., 24ohm). As the load increases, the THD distortion will increase as well. 

    switch said:
    The output of the OPA1688 is 866.9mV with a THD+N of 28.15%.

    With 24ohm load, the OPA1688's output drooped significantly - meaning the op amp is unable to delivery the required current at load. 

    If you have to drive heavy load, then you may have to consider OPA1622. Even with OPA1622, you still need to watch out the output source/sink current over temperature.

    If you have other questions, please let me know. 

    Best,

    Raymond