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TINA/Spice/VCA810: About VCA810 Noise

user3656305
Prodigy 20 points
Part Number: VCA810
Other Parts Discussed in Thread: TINA-TI, , LMH6514

Tool/software: TINA-TI or Spice Models

problem description:

I test the noise above circuit ,input Vi is connected to ground.

In the Two condtions,

1:when Vc is 0 V(VCA=0 dB),There is almost no noise.The minimum resolution of the oscilloscope is about 4 mV, and the current VPP display is 4 MV.

However, when the gain increases to 100 times

2.and Vc is -2V(VCA=40 dB)，The oscilloscope shows that the peak value of VPP is 7-8 VPP.

Through this comparison, can we consider that the minimum recognition input signal resolution of the device is 30 ~ 40 uV?

In our application, the minimum acquisition signal is uV. According to this test, our effective signal is unrecognizable? I don't know what's wrong, or is this the case with the chip?

Seek help！

  • 0
    TI__Genius 15476 points
    Hi Charles,

    This is really a fixed gain amplifier with a variable attenuator, so the SNR should be constant across different gains, even if the total noise is smaller for Vc=0V, which should be -40dB.

    This this device does have a lot of noise; you will likely need to use strong filters to get the SNR sufficient for uV resolution.

    Best regards,

    Sean
  • 0 in reply to Sean Cashin
    Prodigy 20 points

    Hi  Sean!

    Thank for your reply!

    Can you recommend a device that is similar to the VCA810 function and less noisy than it is?

    Make sure my effective signal (Min=1~2uV) is not submerged in the noise,

    thank you very much!

    Best regards

    Charles

  • 0 in reply to user3656305
    TI__Genius 15476 points
    Hi Charles,

    Are you able to use a digitally controlled amplifier? You only need analog if you need to minimize the phase delay. You could look at the LMH6514 instead.

    Best regards,

    Sean