Re: [理工] [電子]-回授

[Maxwell5566 (none)]

※ 引述《serflygod (serflygod)》之銘言：
: http://i215.photobucket.com/albums/cc91/serflygod/007-2.jpg
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: 如題
: 我算出來的跟答案不同
: 不知道哪裡錯了
: 懇請指點

因是是shunt-shunt：

open-loop gain

Vo
--- = (-gm)(Rs//RF)(Rd//RF)
Iin

       -1
beta = ---
       RF

close-loop gain

Vo     (-gm)(Rs//RF)(Rd//RF)RF
--- = -------------------------
Iin    RF + gm(Rs//RF)(Rd//RF)

Vo     1    Vo      1    (-gm)(Rs//RF)(Rd//RF)RF
--- = --- x ---  = --- x -----------------------
Vin   Rs    Iin     Rs   RF + gm(Rs//RF)(Rd//RF)

                    (1)   (2)

(2)的分子有(Rs//RF) = (Rs*RF)/(Rs+RF)跟 (1)分母的Rs 消掉

所以剩RF/(Rs+RF)

(2)在上下同乘(Rs+RF)/RF

就可以得到

Vo       (-gm)(Rd//RF)RF
--- = ---------------------
Vin   Rs + RF + gm(Rd//RF)Rs

參考看看囉

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推 orz3qonz:跟我算的一樣..應該是對的..