本帖最后由 zyboy 于 2013-2-26 15:35 编辑
我是看下面**，不知道当输入端接入电阻RD时，运放公式有如何变化，是怎么得到新公式，感觉运放输入两端接一电阻，对运放输出好像没有什么影响
Noise-gain manipulation: A powerful way to maintain stability in low-frequency applications-often overlooked by designers-involves increasing the circuit's closed-loop gain (a/k/a "noise gain") without changing signal gain,thus reducing the frequency at which the product of open-loop gain and feedback attenuation goes to unity. Some circuits to achieve this, by connecting RD between the op amp inputs, are shown below. The "noise gain" of these circuits can be arrived at by the given equation. ![]() Since stability is governed by noise gain rather than by signal gain, the above circuits allow increased stability without affecting signal gain. Simply keep the "noise bandwidth" (GBP/ANOISE) at least a decade below the load generated pole to guarantee stability. ![]() One disadvantage of this method of stabilization is the additional output noise and offset voltage caused by increased amplification of input-referred voltage noise and input offset voltage. The added dc offset can be eliminated by including CD in series with RD, but the added noise is inherent with this technique. The effective noise gain of these circuits with and without CD are shown in the figure. CD, when used, should be as large as feasible; its minimum value should be 10 ANOISE/(2 pRDGBP) to keep the "noise pole" at least a decade below the "noise bandwidth".
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