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AFE5809: Noise Figure Analysis

Jayaraj Kidav
Prodigy 10 points

Part Number: AFE5809

Hi,

I am performing a design by using AFE5809 chip. My sensor source impedance is 4.5 KOhm. The following are the clarifications required.

1) Whether I need to use an external termination for proper coupling of the sensor signal to AFE (the sensor dynamic range is 1uV to 20mV)

2) How to select the Noise Figure of LNA for various gain configurations (12,18 and 24dB) . Kindly note my source impedance is 4.5 KOhm.

Regards,

Jayaraj

  • 0
    TI__Expert 6040 points

    thanks for using 5809! as datasheet shows , the best noise figure is achieved by using no termination case.  the passive or active termination is mainly for impedance matching if there is a long cable refer to signal wavelength of 50 to 200 ohm and source impedance as 50 to 200 ohm. in your case, the sensor is 4.5K and not likely you can find a 4.5K cable for impedance match. 

    in this case, we suggest you using no termination for best NF. 

    typically 24dB LNA has the lowest NF. 

    Thanks!