supermoment
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typical cmos LC tank (pmos + nmos cross coupled) can oscillate well without current source at the bottom or at the top, the output swing can reach rail2rail without problem.
I just wonder why some designs, current source is added at the bottom, making it current limiting. Besides this, it needs a ac bypass cap for ac ground.
The only reason i could think of is to make it insensitive to vdd since current is defined?
thank you.
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