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A linear transconductance for OTA-C filter

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afujian

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I just don't understand why the parallel differencial pair can increase the linearity of the OTA, who can tell me why?
 

LvW

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When you say "increase" you compare the linearity of two different concepts. Therefore: What is the other design (with smaller linearity) ?
 

wpchan05

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it is a technique of multi-tanh for bipolar linear transconductor.
 

erikl

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... why the parallel differencial pair can increase the linearity of the OTA?
Because of the summing of 2 currents from 2 pairs with slightly different - yet controlled - offset voltages (due to the K ratio). Works correctly only with BJTs or MOSFETs in weak inversion. See the visualization in the PDF below:
View attachment multi-tanh-linearization.pdf
 
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afujian

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I am sorry about the cofusion,I am comparing the singal differencial pair such as Q10 and Q11.
 

FvM

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Q10/Q11 isn't a differential pair. Please notice that they are operating on two separate current sources. I think, the explanation in the linked paper is rather graphic.
 

afujian

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Q10/Q11 isn't a differential pair. Please notice that they are operating on two separate current sources. I think, the explanation in the linked paper is rather graphic.
OK,I mean to compare with the single differential pair.
 

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