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ADL5561 OIP3 vs Pout

In the specification section for 140Mhz OIP3 is +39dBm for AV = 15.5 dB, RL = 200 Ω, VOUT = 2 V p-p composite (2 MHz spacing), but figure 13 shows another results. Why it is so ? 

In my point of view 2 V p-p composite (RL=200Ohm diff or not ?) = 4dBm per tone ? And what the difference between   2 V p-p composite  and 2 V p-p envelope?

  • Hi,

    For the ADL5561 and similar parts, because they are specified with a 200-ohm load, the dBm specifications are with reference to this impedance and not 50-ohms.


      Yes, composite is the same as envelope.  So 2Vpp composite is 1Vpp/tone for a two-tone sinewave test

    1. However, because the part is specified with a 200-ohm load, Pout(dBm)/TONE is calculated as 10*log10(0.5*0.5/2/200/1m) = -2dBm
      1. Note: OIP3 in dBm is also plotted with reference to a 200-ohm impedance

     This does make the number for OIP3 in the specification table look a little conservative.

     OIP3 = 39dBm

    IMD3 = -96dBc

     If the numbers above are correct, then OIP3 from IMD3 would be

    -2dBm(200) + 96/2 = 46dBm(200)   vs 39dBm specified in the specification table.

    IMD3 = -96dBc looks reasonable from Figure 12, but I cannot figure out how 39dBm was arrived at.


    Warm Regards,


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