What is the Linearity of OTA

Hello

Can anyone tell me what is the linearity range of an OTA without using any linearity improvement technique.
In many research papers the linearity of OTA is improved because the linearity of OTA is low. How low is the inearity of OTA. Why do we need highly linear range OTA? What is the advantage of having high linearity?

Regards

What is an "OTA"? Google says it is an "Optical Telescope Assembly" but its design determines its linearity.

Are you referring to an Operational Transconductance Amplifier?

The linearity range of an OTA depends on its

• ICMR
• input voltage, supply voltage, and gain
• needed linearity by the application (e.g. as max. THD value)

crutschow said:

Are you referring to an Operational Transconductance Amplifier?

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Yes OTA= Operational Transconductance Amplifier

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@eirkl- It means if linearity depends on gain then if gain is less than linearity will be less. Am I right? Does it also depend on its output swing

Linearity of any amplifier is one of the most important parameter.
In words: It is nothng else than the degree of linearity between the output signal and the input signal.
In case of an OTA it is the (quasi)-linear dependence of the ouput current Io as a function of the diff. input voltage Vdiff.
An IDEAL OTA has the transfer function Io=gm*Vdiff with gm=const.
In reality, the value of gm can be kept (nearly) constant in a relatively small range of the transfer function only.

simplsoft said:

@eirkl- It means if linearity depends on gain then if gain is less than linearity will be less. Am I right?

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Generally yes. More exactly linearity depends on the relation (open-loop-gain/closed-loop-gain).

simplsoft said:

Does it also depend on its output swing

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Sure: As closer the output voltage signal reaches the supply rails, as less open-loop-gain you can expect. This causes linearity reduction, and due to this non-linearity of the linearity characteristic harmonics of the signal will be generated (as well as inter-modulation products in case of more than one input signal with different frequencies). All this THD = total harmonic distortion contributes to even more non-linearity.

Additionally, both open-loop-gain & closed-loop-gain depend on frequency ...

So if you have to specify the linearity (or more usual: the non-linearity, which means deviation from linearity, often given in %) of an OTA, you'd have to specify also the parameter limits (i.e. the ranges), for which the stated max. non-linearity value is valid:

• ICMR (input common mode range)
• output voltage range (minimum is limited by noise: SNR)
• load impedance
• frequency
• temperature