Re: [問題] 電路板電源設計與Offset
※ 引述《cpyi (cpyi)》之銘言：
: 最近在做一個雜訊量測的系統，因為Gain很大，所以必須要考慮Offset的問題
: 但是一直量不到Datasheet上的額定值，剛好查到一個影片：
: https://www.youtube.com/watch?v=YeNpd-sXaHk
: 他發現Offset跟供電與Bypass電容有關，本來好像會有下集解釋為什麼，
: 但是我找不到那個影片，實際測試我的設計發現真的是如此，
: 機制好像跟Chopper消耗電流以及電源配置相關，但查資料查不太到
: 而且實測不只電容數值大小有關，連放的位置都有關係，
: 有大大有相關經驗嗎？還是有其他書可以作為參考？
: 謝謝！
下面有解答:
That is very easy. Just remove the capacitor on the negative supply and it
will work fine. Why is that: when chopping there flows a small switching
Charge (e.g. 1pC) through the negative supply. This is not a problem, but
when you add your capacitor it will translate this charge to a constant error
voltage. In case of split supply your supply tries to compensate and this
amplifies the error. You should have analyzed it with an oscilloscope not a
multimeter. For any part which is designed for single supply it is a very bad
idea to place a cap on the negative supply.
希望對有興趣的人有幫助
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