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LMX2581 output amplifier biasing

Anthony Williams1
Prodigy 40 points

Is it OK to wire the unused side of RFout A or RFoutB direct to +3.3 volt supply in single ended application?

Are the RF output amplifiers differential pairs?

Must I use the same bias component in both sides (inductor or resistor)...why is this?

 

Thank you

A. David

  • 0
    TI__Mastermind 28001 points

    David,

    I do not think that this is a good idea.   If these are unbalanced, then this will impact the output of the side you do care about.  If you wire direct to 3.3 volts, this looks like a short, not 50 ohms or high impedance (Depending if you use a resistor or inductor).  If it is unbalanced, the harmonics will get much higher and I am not sure what else this impacts.  We have not done much evaluation on this.

    In fact, if one side is used and the other isn't, try to make the load seen by the unused side the same.  For instance, if the used side has a 50 ohm load, put a 50 ohm resistor on the unused side.

     

    Regards,

    Dean