Efficiency of RFMD,s RF6886 HPA

Discussion in 'Wireless & RF Design' started by Pritesh797, Dec 17, 2013.

  1. Pritesh797

    Thread Starter New Member

    Dec 17, 2013
    1
    0
    Hello,

    We are using RF6886 power amplifier in our application. We tested RF6886 for our application. But we got very less efficiency. Current consumption was very high. The gain was also not constant. Gain was constantly decreasing.

    Operating Voltage : 3.3 V
    Frequency: 437.025 MHz
    Output Power: 1 Watt
    Current : 1.92 A
    Efficiency : 15.78 %

    Input power fed to the HPA was swept from -20 dBm to 5 dBm. It was found that the gain was constantly decreasing. In the starting, at lower power, gain was about 33 dB. But as i/p power was increased the gain dropped to about 25 dB at output power of +30 dBm. The rated 1 dB compression point js at 34 dBm. So we weren't able to get 1 dB Compression point.

    The schematic is used from the datasheet. The layout is exactly same as the evaluation board. We used the gerbers of evaluation board to make the layout. We have used thermal vias under the thermal pad for heat dissipation. But still temperature of the board rises in some time.

    How could such low efficiency be explained? What could be the reason for constantly decreasing gain? And why is the current consumption so high?

    It would be really very grateful if you could help us try find solution to this problem. Are there any methods to increase the efficiency and hence decrease the current consumption.
     
  2. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    do you really need a linear amplifier? a class b or c amp would be more efficient.that amplifies is operated in a saturated mode, draws high current. if you are using a pulse, fm, or phase shift keyed signal, you dont need class a.
    cliff
     
  3. iLLbeFrank

    New Member

    Apr 9, 2014
    1
    0
    Hi Pritesh797,

    We are using the same PA and have had similar issues and in trying to find a solution I came across your post. Did you solve your problem in the end? We have managed to steadily increase performance to 33 dBm output at 3.6V supply, 3.2V bias, 43% efficiency. I am curious to hear what you found.
     
  4. alfacliff

    Well-Known Member

    Dec 13, 2013
    2,449
    428
    impedance matching for the antenna will help output and heating problems.
     
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