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When would IC use De-Emphasis instead of Pre-Emphasis or not ?

York Chen
Prodigy 10 points

As we know there are De-Emphasis and Pre-Emphasis tech for high speed signal to eliminate signal distortion.

But I have a question that when would IC use De-Emphasis instead of Pre-Emphasis or not ?

Is  De-Emphasis more popular than Pre-Emphasis ? Why ??

Thanks.

  • 0
    TI__Mastermind 43795 points

    Hi,

    From a Tx equalization point of view pre-emphasis and de-emphasis perform exactly the same function.  They compensate for channel losses between the Tx and connected Rx.

    Almost all current devices use a form of de-emphasis where the maximum output swing is specified.  Then portions of the waveform amplitude are altered to implement a 3-tap or 4-tap filter on the Tx output.  This architecture is easy to implement within a modern CMOS process.  Many standards have utilized this output equalization technique.  The de-emphasis waveform has been defined in many serial protocols including Ethernet, PCIe and SAS.

    Regards,

    Lee