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OPA810: Large-Signal Frequency Response vs Output Voltage

user5973224
Prodigy 220 points
Part Number: OPA810

Hi,

can you please tell me, how you measure the "Large-Signal Frequency Response vs Output Voltage". Its's Figure 7-5 in the datasheet. 

A picture of the measurement setup would be very nice.

My problem is, that i measure a damping in the amplification of 10 % by a frequency of 1 MHz and a propagation delay from 50 ns. I use the OPA810 as an buffer amplifier.

Thank you very much,

 Jan

  • 0
    TI__Genius 15555 points

    Hello Jan,

    Can you provide a schematic? How large is your input/output signal and what are your load conditions? What supplies are you using here?

    Can you also clarify if this is only the case with your large-signal response? Or are you seeing a decrease in gain for small signal as well?

    For the large signal response measurement, the OPA810 is also set in a buffer configuration along with a load condition of 1k-ohm and 4.7pF.

    Best,

    Hasan Babiker

  • 0 in reply to Hasan Babiker31
    Prodigy 220 points

    Hi,

    I use the OPA810 in a standard buffer configuration with an open load. So the load is infinite.

    I see a decrease i gain not only for large-signals. I see the decrease for small signal as well. My inputs voltages reaches from a few milivolts to 3 volts.

    My supply voltages are +5V and -5V. I used the bypass condesators like it is desciribed in the datasheet.

    Do you think its a problem because i dont have a load?

    Or the problem is the Osziloskop and the probe i use?

    Thanks for your help,

    Jan

  • 0 in reply to user5973224
    Guru 140200 points

    Hi Jan,

    sounds like you have a damaged scope probe?

    I would not measure directly at the output of OPA810. Instead, insert an isolation resistor of Rs = 100R as shown in figure 8-1 of datasheet.

    Also, use such a spring probe for all your HF measurements:

    Kai

  • 0 in reply to kai klaas69
    Prodigy 220 points

    Hi Kai,

    thank you for your help. I inserted a load resistor at the output. Now i dont measure a damping in gain.

    Thanks for your help.

    Jan

  • 0 in reply to user5973224
    Guru 140200 points

    You are welcome :-)

    Kai