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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Zero in Common sourse amplifer https://designers-guide.org/forum/YaBB.pl?num=1135062393 Message started by hjzs18 on Dec 19th, 2005, 11:06pm |
Title: Zero in Common sourse amplifer Post by hjzs18 on Dec 19th, 2005, 11:06pm Hi, all; suppose i have a garden-variaty common source amplifer , and also suppose i put a Miller compensation cap,say Cc , between the drain and gate, now i add a zero to my system and the value is Gm/Cc, i wonder if anybody here can give me an intuitive explaination why it is this form.how to think of it. in Razavi's book, he gives a explaination, it is something about current flowing back from the output. but i just can not get it Thanks all |
Title: Re: Zero in Common sourse amplifer Post by vivkr on Dec 24th, 2005, 7:03am Hi, At a zero, the output is zero for a finite input Vin. This only happens at one frequency and so there is no physical short. This can only happen if the current through the two parallel branches cancels out exactly, and no net current flows into the load. Setting Vout=0, path1 gives -Gm.Vin current into the load, path2 gives +sCc current into the load. Net zero current => s=Gm/Cc (RHP zero) Regards Vivek |
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