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Amplifiers with larger load capacitance

Wen Huang
Prodigy 50 points
Other Parts Discussed in Thread: OPA4350, OPA4353

Could you give me a few recommendations for the amplifier with large capacitive load driving capability? I would want a quad opamp with 16 pin SOIC package; and Vs is +/-5V. Thanks.

  • 0
    Prodigy 50 points

    Sorry, I meant 14 pin SOIC.

  • 0
    TI__Guru 63050 points

    Huang,

    A "large" capacitive load is a relative term - you need to be more specific.  Are you talking about few nano or micro-farad?

    The only op amp I know that can directly drive several uF capacitive load is OPA4350 but it is 5V (or +/-2.5V) and not 10V supply part you asked for.  You can improve the capacitive load drive of any op amp by adding a small (10ohm to 50ohm) series output resistor but this may create a gain error if your application involves a resistive load. 

    To get around this problem, a dual feedback configuration shown below will dramatically improve the capacitive load drive of any op amps at the price of significant decrease of its effective bandwidth.

  • 0 in reply to Marek Lis
    Prodigy 50 points

    Thanks for the reply.

    I am using OPA4353, but I need to change it to 10V supply and trying to find a replacement. I can change the circuit to what you suggested. But I want to try without re-layout the board first. The  Cload is about 0.1~0.33uf, could you suggest something as good as possible? If not enough, I'll change the circuit.
    Thanks
    Wen Huang
  • 0 in reply to Wen Huang
    TI__Guru 63050 points

    Wen,

    OPA4353 is an untrimmed version of OPA4350 which I previously suggested for driving high capacitive loads but I have no comparable part to suggest for 10V supply.  If you have no resistive loading, you may just need to add a series output resistance to improve the capacitive load capability of any op amp; otherwise, you may have to implement the dual feedback solution shown in my previous post.