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linearity of a circuit

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ananthesh bhat

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Hi all,

I'm designing a filter for which the linearity is of higher importance. I noticed that linearity will increase if I have higher current in my circuit legs.

But I wanted to know on what all parameters the linearity is mainly dependent?


Is it dependent on gain and phase margin of the opamp I have used? Or is it dependent on the common mode feedback circuit?

Please help me here.

Regards,
Ananthesh
 

For a given amplifier configuration, linearity of a circuit depends on signal amplitudes only.
And the amplifier should have sufficient signal feedback.
The last requirements requires low opamp gain (e.g. Sallen-Key configuration or GIC topologies)
 

LvW said:
For a given amplifier configuration, linearity of a circuit depends on signal amplitudes only.
And the amplifier should have sufficient signal feedback.
The last requirements requires low opamp gain (e.g. Sallen-Key configuration or GIC topologies)
Click to expand...

Based on my experiments, I can say that for Sallen-key, the linearity increases with the gain of the opamp used in the loop. So its difficult for me to agree with you on that point.

And you have mentioned about ample feedback. Does that mean I should have large phase margin?
 

It is a well-known fact that negative feedback increases linearity (improves the THD).
 

20150619_172348.jpg


Please find the attached image. I'm measuring the IIP3 and my specification is 30dbm. I'm reaching the specification. But I'm seeing peaky behavior in the third order harmonic. Is this IIP3 curve plotted is correct or not? Can anybody answer this?

Thanks
 

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