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TLV9001: Open-Loop Gain and Phase vs Frequency

Part Number: TLV9001
Other Parts Discussed in Thread: TLV9002

Hi Team,

In the Open-Loop Gain and Phase vs Frequency characteristic seen in the datasheet Figure 7-9, the phase starts at 100°.

Other operational amplifiers also often start at 90°.
How is phase defined?

Usually depends on the input, but I thought it was 0 or 180 degrees.

Best Regards,

  • Hi Tomoaki,

    nearly all OPAmps even start at 180°, if you only go deep enough with the frequency Relaxed



  • Dear Kai

    Thank you for your reply.

    The simulation also showed that where the frequency is low enough, it will be 180°.

    What kind of circuit is modeled that C3-C5, L2, and L3 show?

    Best regards,

  • Hi Tomoaki,

    C4...C5 are the common mode input capacitances and differential input capacitances of TLV9002, which have to be externally connected to the loop with this sort of phase stability analysis. Otherwise the OPAmp output would not see these input capacitances.

    C2, L2 and L3 are just representations of "ideal" caps and "ideal" inductances.

    The idea of the analysis is to stimulate the inputs "IN+" and "IN-" of OPAmp by the help of "VG1" and to look what comes back to the inputs "(IN+)" and "(IN-)". The dampening and the phase between the input signal and the returned signal is used to make the "Open-Loop Gain and Phase vs Frequency" plot and to calculate the phase margin.

    You might also want to watch these TI's training videos:


  • Dear Kai

    Thank you for your thoughtful response.

    The video in the link is difficult to follow, but once I understand it, it will be very useful.