TLV9061: About definition of "Common-Mode Voltage"

Shiga Yuichi

Prodigy 80 points

Part Number: TLV9061
Other Parts Discussed in Thread: TLV9062

I would like to check the definition of "Common-Mode Voltage" at Figure.4

This word " Common-Mode Voltage" does mean belows?

This figure was taken from another site.

AR# 44954: 7 Series XADC / UltraScale SYSMON - アナログ入力範囲 (xilinx.com)

10 months ago

0 Clemens Ladisch 10 months ago

Guru 270850 points

With an opamp, it is assumed that you have a circuit with negative feedback, and that both inputs are at the same voltage. This voltage is the common-mode voltage.

That ADC figure shows a differential signal; in that case, the common-mode voltage is the average of the two voltages. That definition is more general, but it would hide the actual behaviour of an opamp circuit.

0 Robert Clifton56 10 months ago in reply to Clemens Ladisch

TI__Mastermind 23170 points

Hello Yuichi-san,

Adding to Clemens comments, we have a video series called TI Precision Labs that goes over topics like common-mode voltage in more detail that could help with better understanding op amp fundamentals, if you are interested.

Best Regards,

Robert Clifton

0 Shiga Yuichi 10 months ago

Prodigy 80 points

Thanks for your answer.

Here is another question.

This figure's condition is V+=2.75V and V- = -2.75V.
On the other hand, What kind of characteristics will it have under V+=5V, and V-=0V

0 Robert Clifton56 10 months ago in reply to Shiga Yuichi

TI__Mastermind 23170 points

Hi Yuichi-san,

The device's characteristics would be the same actually, just shift the x-axis. What's important to understand is the offset voltage will shift when the common mode voltage is around (V+) - 1V. This would apply to any supply voltage you are using for the TLV9062.

Best Regards,

Robert Clifton

+1 Clemens Ladisch 10 months ago in reply to Shiga Yuichi

Guru 270850 points

The input crossover happens at a fixed offset from the positive supply, i.e., +2.75 V in figure 4 corresponds to 5 V in your circuit.

0 Shiga Yuichi 10 months ago in reply to Robert Clifton56

Prodigy 80 points

Robert Clifton56 said:
he device's characteristics would be the same actually,

Thank you for your anser. I understood that characteristics of offset voltage shifting.

0 Shiga Yuichi 10 months ago in reply to Clemens Ladisch

Prodigy 80 points

Thank you for your answer. I understood that how to correspond.

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TLV9061: About definition of "Common-Mode Voltage"