AD8352 Evaluation Board

Hello,

I purchased AD8352 evaluation board and tested it as it is for reviewing of amplifier design.

Test conditon was below.

Single power of DC 5.0V, Input to VINP was 20mV@25Mhz by S/G, Output monitor from VOUTP by Oscilloscope using 50ohms cable. and  Enable switch "On".

I don't know why but output waveform reduced to half of input level even gain resistor Rg is 115 ohms(Gain of 10dB).

However I can see calibration circuit at lower side inpur J1 and output J2 was tested OK.

Please advise me.

  • 0
    •  Analog Employees 
    on Feb 18, 2020 1:41 AM

    Hi Iksu,

    Thank you for considering AD8352 on your amplifier design.

    AD8352 is a differential amplifier and the difference between VOUTP and VOUTN should be measured to determine the output properly.
    You're only measuring from VOUTP and this could be the reason why you're not getting the expected result.

    Also, since you're using AD8352 in single-ended input operation, you can take a look on page 12 of the datasheet for the considerations in this mode.
    It's stated that to balance the output you can try to place a 200 ohm resistor between VIP and RGN pins(though the provision is not available based on the schematic).
    The gain equation is also slightly different from differential input mode given as:

    And with the default configuration of the evaluation board (RL  200ohms and RG = 115) you'll have a gain of approximately 13.7dB. This may still vary based on the Distortion cancellation components used.
    Let me know if you still have further concerns Iksu.

    Best Regards,
    Dann

  • Hi Dann,

     

    Thanks a lot for your reply.

    I understand AD8352 is a differential amplifier to measure difference between VOUTP and VOUTN.

    However what I would like to know is if we test AD8352 EVM as it is without any modification, then it is not operated properly?

    If we see the circuit diagram of EVM, R4 and R13 are 0 ohms and those were terminated on both of VINN and VOUTN.

    In my opinion, differential measuring is no meaning if not removed R4 and R13 of 0 ohms and apply other modification.

    Please give me your opinion.

     

    Thanks and regards

     

    Iksu