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Bias controller for HMC6981LS6

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Product Number: HMC6891


We will use an HMC6981LS6 amplifier and we will use an active bias controller to guarantee its correct behavior.

After taking a look at the selection product table for these controllers:

and looking at each of the parts datasheets, I am pretty sure that the HMC981LP3E can meet the HMC6981LS6 specifications.

If I am not wrong the HMC980LP4E also could meet the amplifier specifications (I have to study more in depth its datasheet), but the former is perhaps simpler to configure.

Could you also confirm if I am on the right choice ?

BTW, The HMC981LP3E datasheet states that VGATE High Level maximum value is of VG_MAX = VNEG+4.5 V.

In which case this signal can rise up to VG_MAX ?

I ask this because if I have VNEG set to -3 V,  VNEG+4.5 V could damage the HMC6981, since its gate voltage range is specified from -3V to 0 V.

Thanks in advance,


HMC6981 to HMC6981LS6 in title
[edited by: simon.zz at 3:59 PM (GMT -4) on 12 Aug 2022]
  • Hi Simon,

                     The HMC981 will not provide enough current to properly bias the HMC6981LS6. At what is the highest output power level you plan to operate at?

    The limiting factor with the Automatic bias controllers  is the amount of current that can be supplied to the PA.


    Jim B

  • Hi  ,

    Thanks for your reply.

    Of course you are right, I did not pay attention to the HMC6981LS6 drain current requirements.

    In our project, the HMC6981LS6 drain current will be approx. 1.1 A as datasheet suggests.

    Since the HMC6981LS6 VNEG must be in range of -3 V to 0 V, the HMC980LP4E seems to be fully compliant with the PA. At least this is my intuition.

    Do you agree ?

    Thanks !


  • Hi Simon,

                      Yes, It is compliant. You need to choose your maximum Pout for the HMC6981 so you don't operate at a level where the HMC6981 is unable to supply the proper drain current to the PA.

    This would be a Pout of ~ 32 dBm.

    Attached is a link to the HMC980 wiki page. There is a calculator available for down load to assist in the resistor selection.

    HMC980 Configuration Calculator [Analog Devices Wiki]


    Jim B