Post Go back to editing

Regarding output voltage fluctuation when switching gain

Category: Hardware
Product Number: AD8338

Hi,

I'm considering AD8338.

I am evaluating the AD8338 evaluation board.

When the gain of the AD8338 is changed, a phenomenon occurs in which the output of the AD8338 fluctuates more than the original output.
The same problem occurs with the default circuit of the AD8338 evaluation board (EVAL-AD8338) and with my prototype.
Is this a phenomenon specific to AD8338? Is there a solution?

【input signal】
・10kHz, 0.1Vp-p, single-ended input
・100Hz, 0.3Vp-p, Voffset = 0.4V, J3&J4=Open
→ Under these conditions, the output amplitude increases at the rise/fall of gain switching.

Best regards,

Yuya

Top Replies

    •  Analog Employees 
    •  Super User 
    in reply to Yuya +1 verified

    Hello  ,

    The jumper settings shows that the board is configured as single-ended input to differential output. Normal signifies a differential input to differential output. 

    I hope this information helps…

  • Hi  ,

    Thank you for reaching out and for considering the AD8338 for your application. 

    Regarding the fluctuation you're experiencing when changing the gain, I'd like to gather a bit more information to better assist you. When you tested the AD8338 using the EVAL-AD8338 board, did you set it up with a single-ended input to a differential output configuration? This setup typically involves using the ADA4940-1 as a differential driver amplifier.

    Could you please confirm how you've configured the inputs and whether the ADA4940-1 is part of your setup? Also, can you share your scope shots in the output. This information will help us to pinpoint the cause of the fluctuation and find a solution for you. 

    Thanks,

    Mae

  • It appears that the above question has been answered already so I'm temporarily closing this thread. In case there are additional questions, feel free to reply to this thread. Thank you!

  • Hi, maarmas

    Thank you for answering! And sorry for the late reply.

    The jumper settings for each are listed below.
    J5: Connect the lower two
    J6: Connect the upper two
    J7: connect two
    J8: connect two
    (Settings are as shown on the silk sheet, SE->DE)

    Is Normal a single-ended input?

    Scope shots cannot be posted here. sorry.

    Best regards.

    Yuya

  • +1
    •  Analog Employees 
    •  Super User 
    in reply to Yuya

    Hello  ,

    The jumper settings shows that the board is configured as single-ended input to differential output. Normal signifies a differential input to differential output. 

    I hope this information helps.

    Thanks,

    Mae