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  1. #1
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    How to increase the gain-BW of a two-stage op-amp?

    Hi everyone,,,,,,,,can anybody help me in increasing the gain-BW of an op-amp,and also gain.......

    Do i want to use any other configuaration added to two-stage opamp......

    Plz Help me out....

    •   Alt24th April 2010, 06:45

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    Re: How to increase the gain-BW of a two-stage op-amp?

    I don't know if this will work right, but according to my deduction, it seems like this:

    Av1 = gm1*ro1; Av2 = gm2*ro2, first pole is about: 1/(ro1*gm2*ro2*Cc)

    gm1, gm2 is the first and second stage transconductance
    ro1, ro2 is the first and second stage output resistance
    Cc is the miller compensation capacitance

    So GBW is about Av1*Av2*pole1~gm1/Cc
    that is increase the first stage transconductance and reduce the miller compensation

    For the gain, you should make gm1*ro1*gm2*ro2 to be very large. And because gm1 is proportional to sqrt(I1), ro1 is proportional to 1/I1, and same as gm2 and ro2. Finally, you have to make 1/[lamda1*lamda2*sqrt(I1*I2)] large。

    lamda is the channel modulation coefficient of mos transistor. Larger length of MOS has smaller lamda.

    At the end, it's your tradeoff between all the parameters.

    I think generally it is very hard to construct a two stage opamp with large bandwidth comparing with other structures.

    Alvays



    •   Alt26th April 2010, 06:10

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  3. #3
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    How to increase the gain-BW of a two-stage op-amp?

    pole-splitting compensation/Miller compensation & right-half-plane zero cancellation always used at design.



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