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LMH6401: Inquiry for thermal gain control

Takanori Yuzawa
Intellectual 1490 points
Part Number: LMH6401


Hi team

Voltage gain seems to be 1kHz=26dB, 100MHz=26dB at gain=10 from thermal frequency control on the datasheet P29.
And also, it seems to be 1kHz=25.93dB, 100MHz=26dB at gain=10 from thermal gain control.
Do you know the reason why it has difference at same gain setting?
Voltage gain has the difference of 0.17dB when thermal control does not active. Is ti correct?

Best Regards,
Takanori Yuzawa

  • 0
    TI__Genius 13935 points

    Hello Takanori-san,

    The two graphs do not have the same color code.  You can see that in Figure 61 there is one Thermal gain correction curve that is 26dB at both low and high frequency.  In Figure 62, this same thermal correction gain setting is used while the frequency of thermal correction register is swept. 

    There are two separate settings available, one is the thermal correction gain register, and the other is the thermal correction frequency register.  There were too many combinations to show them all, so each graph has only one setting from the non swept register. 


    It looks like the Gain = 10 and frequency = 9 is very close to the best overall solution.  


    You are correct, the gain error due to the internal thermal time constants is 0.17dB.  It is possible to correct this at low frequencies, but there is a transition zone where the error cannot be totally eliminated. 

    Regards,

    Loren