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LMH6521: LMH6521 gain problem and the output questions

Part Number: LMH6521

I use LMH6521 for the small siganl. 

the input signal is  300mV ( differantial ), and it's common mode voltage is 2.5V

and LMH6521 output common mode voltage is 4.4V . is that correct ?

the gain register is 0x80 , it means the gain is 26dB.


when i add a 0.1uH inductance  to the output between the out + and the GND , the out- and the GND.

the output res is 50Ω, and with a 0.1uF cap series connection .

the output siganl become very small . it seems less than 100mV.


without the inductance , res and cap . i can get 1.2V signal output .

Question :

does the output signal common mode voltage correct ? 

why i just get 12dB gain when i use nothing on the output ?

why the signal is become very small when i use the recommend circuit ?

how can i get the 26dB gain ?

  • Hi, 

    Would you be able to send me a schematic of the input and output circuits you are using for the device? Is this on the evaluation module? 

    You will need the inductors on the output to properly bias the output stage, that is why the common mode voltage is very high when you do not have them.