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THS4521 - TINA simulation important results differences

Cezar Morun71878
Prodigy 170 points

In simulation I've got a gain of 1/3.4 as expected, however on the real board the gain is 1/4.75 (I'm using this op amp as an active divider).

Unfortunetely I was not allowed to attached the TINA. Is any way I can do it on this forum?

Regards,

Cezar

  • 0
    TI__Genius 17905 points

    Cezar,

    You should be able to click on the paperclip icon and browse for a file on your PC. I regularly attach TINA schematics to my posts without issue.

    I believe you are in contact with one of our field apps engineers and he has forwarded me your TINA schematic. Here are my comments/questions/suggestions:

    1) I see that you are AC coupling your signal. If that is the case, there is no need for the 5V reference (V1). Have you tried disconnecting the 5V reference so that R219 (3.4kohm) is simply connected to the 1uF capacitor to ground?

    2) Also, have you verified that all of the resistor values are correct?

    3) How do you measure the gain? Are you using an oscilloscope to compare the single-ended input and the differential output (maybe with a differential probe or using scope math)? Please make sure you do not have any scale factors programmed into your oscilloscope.

  • 0 in reply to Kris F
    Prodigy 170 points

    Hi Kristoffer,

    1) I used AC and DC (replaced C4 with a 0 Ohm resistor) coupling. Similar not expected gain. I need to have the 5V ref., however, I think it should have no influence on the amp. gain.

     2) I double check the resistors values before contacting Leonard and they were correct.

    3) I used all combinations of single ended and differential probes and the scope math and the scope was correctly set.

     

  • 0 in reply to Cezar Morun71878
    TI__Genius 17905 points

    Cezar,

    Can you please send oscilloscope captures showing the single-ended input and each output (single-ended measurement)?

    If you are AC coupling, you do not need the 5V reference on the inverting input side because the 5V offset of the input signal is not passed to the amplifier.

    Is the gain always 1/4.75 even if you reduce your input signal amplitude? Otherwise, the signals at the outputs are not clipping or visibly distorted, are they?

    Perhaps it is easier if we communicate directly. Please e-mail me at k.flores@ti.com with your contact information.