[問題] OP-amp用於unity gain buffer的設計
請問"要下線"的OP-amp的問題
我現在在做一個用於DAC末端的unity-gain buffer用的OP-amp
採用的OP-amp架構是2-stage cascode OP(為了達到High Gain以及wide Outswing)
單端輸出,當unity gain buffer的準確率要80dB,頻寬要1MHz,
因此放大倍率我設計在80dB以上,TT時81dB,當我在跑corn發現了問題。
在FF,FS,SF時,原來的80dB會掉到70dB,由於第二級的輸出電壓漂離我設定的0.9V的關係
(第二級輸出電壓其實很受第二級下端NMOS的gate電壓的影響)
想請問這種用於unity-gain buffer的OP-amp,能不能加CMFB去鎖住OP-amp的輸出
以及gate?
有什麼單端鎖定的CMFB可以使用嗎? 到目前看到的CMFB都是用於雙端輸出用的...
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