Post Go back to editing

ADPA1107 Gate Bias

Category: Hardware
Product Number: ADPA1107

Working with the ADPA1107 in a pulsed drain configuration. I need to create a -2.7V bias for the gate. 

Is there a recommended way to achieve this bias voltage and have it as stable as possible?

Thus far I have been trying to do this with a switch-mode DC-DC converter however the switching noise is a problem. The current supply I am using has at best about 250mV (peak to peak) of switching noise. I am worried that this will be a problem in operation as  there is only a small margin for the gate bias before it reaches its "off" condition. Also will the switching noise damage the amplifier? or will the RF gain become a function of these voltage transients?

Thanks

Parents
  • Hi Eric,

                      Could you send me your schematic so I can se how you ar pulsing the gate? Why did you choose gate pulsing instead of drain pulsing? Normally we pulse the drain of GaN amps. Although it is acceptable to pulse the gate.

    Regards,

    Jim B

  • I am pulsing the drain.

    However I still need to create the stable -2.7V bias. I am having trouble with getting a negative bias with very low ripple from a switch mode DC-DC converter

  • Hi Eric,

                         What devices are you using to generate the negative bias? Sound like you need to add capacitance or get a cleaner supply. What capacitance do you have on your gate. If you can share the part numbers?

    Regards,

    jim B

  • Hi Jim,

    I am using this DC-DC converter: PDQE10-Q24-D9-DIN

    It creates a -9V supply, which I put through an RC lowpass filter. (3 section filter with 0.16uF, 0.033uF, and 6.8nF capacitors) I have tried larger values aswell, however these are best results. 

    After the filter I have tried simply using a voltage divider, also using a linear voltage regulator, and finally using an opamp to create the proper bias. All 3 ways seem to be only as stable as the -9V supply.

     

    Is there a standard way to get this bias? possibly without using a switch mode DC-DC converter?

    Thanks

  • Hi Eric,

                      What power supply are you using to drive the dc to dc converter? The noise spec on the converter is 80 mV p-p. Maybe the issue is being caused by the power supply used to drive the dc to dc converter. 

    In the lab normally use Keithley 2400 to drive the gate.

    I am checking with the power group for a recommendation for a suitable LDO to generate the negative voltage.

    Regards,

    Jim B

  • Hi Eric,

                 Here is a low noise LDO that should work to provide the gate bias needed for the ADPA1107.

    LT3093 (Rev. 0) (analog.com)

    Regards,

    Jim B

  • Hello, 

    Moving this thread to the RF and Microwave Community.

    Regards,
    Paul

Reply Children
No Data