OTA Integrators: Choosing the Right One for You

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Discussion Overview

The discussion revolves around the selection of OTA (Operational Transconductance Amplifier) integrators for integrating analog signals, particularly in the context of a dual slope ADC (Analog-to-Digital Converter). Participants explore various types of OTA integrators, their practical applications, and considerations regarding their performance.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • Salil inquires about the types of OTA integrators available and how to choose the appropriate one.
  • Another participant questions the specific integration needs and the purpose of using an OTA, suggesting that the context is important for decision-making.
  • Salil expresses concern about the variability of transconductance (gm) with large input signals in the context of integrating for a dual slope ADC.
  • A participant suggests that a traditional solution would be a Miller Integrator, referencing a Wikipedia page for further information.
  • One participant expresses doubt about the availability of OTAs as off-the-shelf components, noting their limitations in driving resistive loads.
  • Another participant confirms that op-amps are typically preferred for this application due to the issues with OTAs, reiterating the suggestion of using a Miller Integrator.
  • A list of specific OTA models is provided by a participant, indicating that some OTAs can be sourced for practical use.
  • A participant acknowledges a correction regarding the availability of OTAs, indicating a shift in their understanding.

Areas of Agreement / Disagreement

Participants express differing views on the practicality and availability of OTAs, with some suggesting they are not typically available as standalone components while others provide specific models. There is no consensus on the best approach for integrating large signals with OTAs, as concerns about gm variability remain unresolved.

Contextual Notes

Participants have not fully resolved the implications of gm variability with large input signals, nor have they clarified the specific conditions under which OTAs might be preferable or practical.

Who May Find This Useful

Individuals interested in analog signal processing, particularly those working with ADCs or exploring the use of OTAs in their designs.

salil87
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Hi
What kinds of OTA integrators are available and how should i decide which to use?
Thanks
Salil
 
Engineering news on Phys.org
What are you trying to integrate?
Why do you need to use an OTA?
How will you trigger a reset?
 
I am integrating the Analog signal for a dual slope ADC. But since the input is a large signal won't the gm vary with the input level?
Thanks
Salil
 
I'm not sure you can buy OTAs off-the-shelf... I think they are only useful as internal components in an IC. The problem with an OTA is while you can implement simpler integrators with them in theory, they can't drive resistive loads and are therefore less interesting in practice.
 
salil87 said:
I am integrating the Analog signal for a dual slope ADC. But since the input is a large signal won't the gm vary with the input level?
Thanks
Salil

Yes. That's way people usually use op amps for this type of thing. See Baluncore's post. You want to use a Miller Integrator.
 
analogdesign said:
I'm not sure you can buy OTAs off-the-shelf ...
Look at
LM13600, LM13700, CA3080, CA3280, LM3080, CA3094, LT3469,
OPA460, OPA461, OPA660, OPA661, OPA860, OPA861, OPA2662
NE5517, MAX435, MAX436, NT996,
 
Last edited:
Well I certainly stand corrected!
 

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