LMH5401: CMRR measure for LMH5401

Mickey Zhang

Genius 12080 points

Part Number: LMH5401

Hi team,

The customer is using LMH5401. For the Figure 50 of the datasheet, when the frequency is close to 1GHz,

CMRR is -50dB. The customer would like to measure the -50dB CMRR value when the frequency is close to 1GHz.

Would you explain how to measure CMRR value? Would you send me a TINA circuit to measure CMRR value?

Best Wishes,
Mickey Zhang
Asia Customer Support Center
Texas Instruments

over 8 years ago

0 Jacob Freet over 8 years ago

TI__Expert 8720 points

Hi Mickey,

The CMRR is measured on a four port network analyzer by injecting a common-mode signal to both of the input pins and measuring the effect it has on the differential output.

Regards,
Jacob

0 Mickey Zhang over 8 years ago in reply to Jacob Freet

TI__Genius 12080 points

Hi Jacob,

Would you explain more about the CMRR measurement for LMH5401?

Would you send me a refer circuit or a TINA circuit for LMH5401 to measure LMH5401?

What is the common voltage range for the CMRR measurement?

I note a CMRR measure post：

In this post, our engineer provide a TINA circuit to measure CMRR.

0 Mickey Zhang over 8 years ago in reply to Jacob Freet

TI__Genius 12080 points

Hi Jacob,
Would you continue to support this case? The customer is waiting for my reply.

0 Jacob Freet over 8 years ago in reply to Mickey Zhang

TI__Expert 8720 points

Hi Mickey,

My apologies as I was on vacation. I've attached a TINA model showing the CMRR measurement circuit for the LMH5401. It is actually quite simple with an FDA because you can directly look at the differential output signal compared to a common mode input. Please note that the model does not perfectly capture the high frequency CMRR effects that can be more accurately seen in the datasheet.

Regards,

LMH5401 Common Mode Circuit.TSC

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LMH5401: CMRR measure for LMH5401