circuitking
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Hello,
I am confused whether to use DC analysis or AC analysis to prove the below statements.
Case 1: Im3,4 >Iss
If the current in M3,4, I(M3,4), is high compared with Iss then that means the Vocm is high. To make Iss equal to Im3,4 we increase the Vp of M3,4 such that IM3,4 reduces.
Case 2: Im3,4<Iss
If the current in M3,4, I(M3,4), is low compared with Iss then that means the Vocm is low. To make Iss equal to Im3,4 we decrease the Vp of M3,4 such that IM3,4 increases.
The above logc makes sense to me If I follow the small signal analysis. However, my dilemma is that output common mode voltage (Vocm) is a DC quantity, in that case we should use something like Vop or Vom=VDD-Im3,4*R (resistance of M3,4). If I analyse in this view, the above statements are just opposite. Can someone confirm. Thanks
From: Design of Analog CMOS Integrated Circuits, Second Edition, Behzad Razavi
I am confused whether to use DC analysis or AC analysis to prove the below statements.
Case 1: Im3,4 >Iss
If the current in M3,4, I(M3,4), is high compared with Iss then that means the Vocm is high. To make Iss equal to Im3,4 we increase the Vp of M3,4 such that IM3,4 reduces.
Case 2: Im3,4<Iss
If the current in M3,4, I(M3,4), is low compared with Iss then that means the Vocm is low. To make Iss equal to Im3,4 we decrease the Vp of M3,4 such that IM3,4 increases.
The above logc makes sense to me If I follow the small signal analysis. However, my dilemma is that output common mode voltage (Vocm) is a DC quantity, in that case we should use something like Vop or Vom=VDD-Im3,4*R (resistance of M3,4). If I analyse in this view, the above statements are just opposite. Can someone confirm. Thanks
From: Design of Analog CMOS Integrated Circuits, Second Edition, Behzad Razavi