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OPA2320: Need a Low Offset、Low noise, and Wide bandwith solution

Anna Chiu14
Prodigy 110 points
Part Number: OPA2320
Other Parts Discussed in Thread: OPA2380,

Hi Team,

My customer was use OPA2380 and looking for better noise performance.

Now they use OPA2320 to do testing, and set it up as differential amplifier, gain is 33. The input signal is 50mV sin wave.

When the frequency of sin wave increased to 30Khz and it is getting distortion.

Following is the out put signal when the input at 80Khz.

Please help to advice if you have better suggestion for this application.

  • Guru 140200 points

    Hi Anna,

    what do we see in the scope plot? Input and output signal?

    Can you show us a schematic of your test circuit? Where exactly do you measure?

    Kai

  • in reply to kai klaas69
    Prodigy 10 points

    Hi Kai,

    thanks for your reply

    The input signals are two sine signals with 90 degree phase difference. The amplitude of the sine signals is 50 mVpp ,the frequency is 80kHz and the dc offset  0V.

    The yellow and blue line are the output signal measured from test circuit which is shown below.

    where the offset voltage is 1.5V and signal source is the sine that i mentioned at the beginning part.

  • in reply to user5007768
    Guru 140200 points
    Hi User,

    I see in your schematic a huge capacitive load of C1=47nF. This presents an impedance of only 42R at 80kHz! On the other hand, R5 is too small to isolate the output of OPAmp from this huge capacitive load. So, C1 is short-circuiting the output of OPAmp!

    Increase R5 and decrease C1 to make the OPAmp work properly.

    Kai
  • TI__Expert 5830 points

    Hello Anna,

    I have a couple of questions regarding the circuit provided.  

    1. What are the supplies of the amplifier?
    Is the node of the 47nF load connected to a data converter?
    1. If so,  what type of ADC (Part number)? 
    2. If so,  what is the acquisition and conversion time?
    3. If so,  what is the value of the reference voltage?

    Best regards,

    Errol Leon

    Texas Instruments

    Precision Amplifier Applications

  • in reply to Errol Leon6
    TI__Genius 11135 points
    Anna

    We haven't heard back from you...did this answer your question? If I don't hear back from you in a day or two I will close this thread, but re-open the thread or create a new one if you have any other questions.

    Regards
    Dennis