开关管长度的设计如何考量？

wfcawy

I see little point to optimize the switch size for DCCA in VCO.  It looks funny if your purpose is just to have a larger effective C.
Have you checked whether your equation is correct enough to calculate the effective capacitor when using Port(it is frequency related) ?
if you know Ron/Coff of the switch(Q value, tuning range),  it is good enough for a DCCA design.

JoyShockley

回复 11# wfcawy


   5GHz SP 仿真
   把L 调到0.5u后，即使W=5u。

   开启后接入的有效电容只有70fF，而MIM电容大小是158fF。假设我希望能接入100fF，我应该调节MIM吗？

wfcawy

the imaginary part of Y11 is not purely capacitance, and it is better for you to  make some derivation on imag(Y11) based on the first order assumption of the switch (on: Ron,Con, off: Roff, Coff). it is very helpful to design a reasonable DCCA in an intuitional  way

wfcawy

回复 12# JoyShockley


    70fF is due to the larger Ron, you need to reduce Ron by increase W, usually the Coff is OK to be about 1/10 of Cmim

heeda

回复 4# kwankwaner


    dibl...

jiangyanjin

回复 3# JoyShockley


    L越大，VT越大吧

abonic

回复 16# jiangyanjin

It depends, for long channel devices, Vth increases as Leff increases just as the case in Razavi's textbook,
However, in modern process (i.e. 130nm or 65nm), as Leff increases, Vth increases at first and decreases at
a certain Leff point. Very interesting. This is so called RSCE effect

semico_ljj

进来学习。

semico_ljj

research

ljcfcb

抠得这么细致，学习了！