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Question about PCB design of HMC788A and HMC408LP3E


My customer are considering to use HMC408LP3E and HMC788ALP2E.

And they have some issues to darw PCB artwork related desiding size of pattern.

Please refer below questions and let me know your opinions.

1. HMC408E

  As Page 9 of HMC408LP3.pdf, below TL1 (0.2 inch)  & TL2 (0.1 inch) value are optimized for 5.7 ~ 5.9 GHz operation.

Q1-1)  If  size of TL1 and TL2 are reduced, which specification or performance of HMC408E are changed?

Q1-2) Would you provide your data (or test result) about changed values of HMC408E specificartion?

Q1-3) If they use this device at 5.4GHz to 5.9GHz, would you recommend values of TL1 & TL2?

2. HMC788ALP2E

At page 8 of HMC788ALP2E.pdf , inductance value of L1 is recommded as "Conical 6.35uH.

Q2-1) Why do you use L1 inductor in your evaluation board?

          Is it for supporting wide band coverage?

Q2-2) If they use this device for 5 to 6GHz band only, would you suggest your recommended inductor?

Please advise me.


  • Hi Se-woong,

    For HMC408LP3E,

    We have not tested the performance of the amplifier with different TL combinations. The board configuration with TLs and matching components is the configuration we used to generate the DS plots. Reducing the values of TL1 and TL2 might have a minor effect on Pout.

    For HMC788A,

    Like you said, the conical inductor is used for wideband coverage. For narrowband operation a smaller inductor can be used. 220nH from 0402DF series can be a good starting point. We used similar inductor values from the same series for other amplifiers.