• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 49 subscribers
  • Views 717 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

OPA847: High linearity with a gain of +20 or +10 V/V Amplifier

xyz xyz
Intellectual 1000 points
Part Number: OPA847
Other Parts Discussed in Thread: LMH6629

Hello

I buffered a small signal with a unity gain buffer in the front end of a sensor. the frequency range of the signal is 10KHz to 5MHz.

now I want to amplfy it with a gain +10V/V or +20V/V.

I'm surprised with two ultra-low noise IC such as LMH6629 and OPA847.

but the linearity has a key role in my application. (I have a 14Bit ADC)

at 1MHz: LMH6629 with a gain of +10V/V has a SFDR of 75dBc and with a gain of +20V/V has a SFDR of 71dBc.

as per OPA847 datasheet the OPA847 spice model  can not predict well distortion:

http://www.ti.com/lit/ds/symlink/opa847.pdf page15

http://www.ti.com/lit/ug/tidu016/tidu016.pdf  (a usefull document about OPA847)

But I think the linearity of OPA847 is better than LMH6629.

which one has better linearity?

Regards

  • 0
    TI__Genius 15975 points
    Hi,

    Both the OPA847 and the LMH6629 should be able to meet the 14-bit linearity of the ADC, provided there is filtering involved in-between the op-amp and ADC for anti-aliasing harmonics and noise.

    The OPA847 certainly has better linearity compared to the LMH6629 in the 10kHz to 5MHz range. This is because of the increased supplies of +/-5V for the OPA847 as opposed to only +5V supply limitation on the LMH6629 for the same output swing. Basically, it comes down to the trade-off between burning more power or providing additional filtering.

    Best Regards,
    Rohit