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# How to design a 8:1 mux at 2GHz in 0.18um technology?

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#### sachinmaheshwari

##### Member level 4
how to design 8:1 mux
with specifications
vdd=1.8v
CL=2pF
.18um technology
the circuit should work at 2 GHz frequency

designing of mux

mux can be realised with inverters or Nand gates.
Design these gates(transistors) with the specified load CL=2PF.

designing of mux

You can do it using transmission gates.

Re: designing of mux

i have already designed it through transmission gate but the problem is
the specification
that is
2GHz frequency and CL= 2pF
i am getting the distorted output
wat should be the (w/L)of the transistors.
n
do u know how to calculate the (W/L)'s of the transistors?

Re: designing of mux

dear Dude,

U can't alter the length since ot will be fixed depending on technology

u can alter the width also u can't increase as per u need .

there should be a proper tapering or scaling factor so that the u can

make the design to work with ur frequency and load

phutane

designing of mux

If you are looking for the most efficiency, please refer to the device architecture and manual of synthesis tool.

Re: designing of mux

so where will i find device architecture and synthesis tool manual?

### sachinmaheshwari

Points: 2
Re: designing of mux

but the problem is i have made the deign of 8:1 mux using transmission gate
CL=2Pf
now when i am including CL i am not getting the output.
so wat to do.
n one more thing how do i choose my w/l
ratio.
that is how to calculate W of a transistor.

Re: designing of mux

You can design a basic transmission gate mux and do its layout. Extract the netlist from the layout. Then you can use the sweep command in spice to vary the width of the transistors and the run the simulations for all the widths and get the width that matches your specifications. The only drawback in this method is that the effect of capacitances for each varying width cannot be mirrored. But this method will give you an approximate idea of the width.

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