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Request about OPA551 oscillation measures

Nobuhiro Haruta
Prodigy 230 points

Other Parts Discussed in Thread: OPA551

I am Nobuhiro Haruta of KTL Japan.

I have a question about OPA551 from a customer.

＊The use situation, problem 　

 The circuit of customer oscillates it by +-10V, the 200mA output. 　Customer understood that the output oscillates for capacitive load. 　  Please refer to an attached diagram for the use circuit.

＊Question contents 　

 In Figure10 of datasheet, there is an oscillation restraint method of gain=1 of the negative feedback. 　Customer is curious about oscillation measures method of voltage follower. 　Would you please teach me the measures method in case of voltage follower?

OPA551 customer circuit.pdf

  • 0
    Prodigy 230 points
    Hello All,

    I have a repeated demand from customer.
    I can reply to you if you have any question.
    Would you please reply as soon as possible?
  • 0
    TI__Guru 74191 points

    Nobuhiro,

    Your question refers to OPA551 oscillation caused by the capacitive load but your customer schematic you provided does not show any load. It would also be very helpfull if you could send us a scope picture showing the input as well as output waveforms.

    Fig 10 of the datasheet actually shows the way to boost the output current using the external transistors (see below) but the dual feedback part of the circuit may also be used to improve the capacitive load drive - in such case, however, there is no need for external transistors.

    Attached please see the presentation showing the ways to stabilize the unity-gain circuits in a greater detail. If your customer needs additional assistance, please provide the full circuit schematic showing capacitive/resistive loads as well as the magnitude and frequency of any input signal applied.

    Solving Op Amp Stability - Unity Gain.ppt