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OPA891: TINA-TI - Hybrid Topology Open Loop Sims

Nathan D'Arcy
Prodigy 50 points
Part Number: OPA891
Other Parts Discussed in Thread: JFE2140, OPA2891

Tool/software:

Hello, I have a hybrid differential amplifier topology using the JFE2140 and dual package OPA2891 amplifier. I am trying to simulate some stability analysis but am running into issues getting the open loop sims working. I am testing the common mode half-circuit of my differential amplifier. Does anyone have any insight on how to get a stability analysis in TINA for the below circuit? I have tried injecting the AC source at the JFET gate(input to the hybrid amp) and also at VFB. 

 

  • 0
    TI__Genius 16585 points

    Hi Nathan,

    The best way to test the stability of the circuit is to break the circuit at the inputs. I attached a link below to our Precision Lab videos that shows how to do this. The video that covers this way of testing stability is under the stability section and is called "Breaking loop on differential amplifier." The inputs can be open and is not specific to just a differential amplifier. I would add that with any stability analysis, if the amplifier is not biased appropriately, stability analysis would likely show erroneous results and will not function. The amplifier with just a feedback capacitor would behave as an open and not be DC biased appropriately.

    Precision labs series: Op amps | TI.com

    Best Regards,

    Ignacio