What is the standard MUX size ?

[twonsr]

The standard MUX size.

Dear all :

if in an inverter :
pmos = 9u/1u , nmos=3u/1u

then in an MUX :
pmos = 9u/1u , nmos=3u/1u


Is the setting correct ? or any method to decide the MUX size ?

thank you

 

[Sergiu_Q]

Re: The standard MUX size.

depends of your scheme(you can do a mux in many variants)...post your scheme and we can do a small calcul of your components

 

[twonsr]

Re: The standard MUX size.

my circuit just uses a mux as a switch.

send one of two signal to a comparator's input.

I review my textbook but I can't find any example for a mux's size.

 

[Sergiu_Q]

Re: The standard MUX size.

in the picture you some example of mux...just tell us witch of this you use ..and the calcul will be no problem

 

[jordan76]

Re: The standard MUX size.

Hi twolevel2002,

If my understanding is correct, you need a CMOS switch for your comparator.
In this case the key point is to make sure there is low distortion and acceptable delay. As a rule of thumb, equal size with minimum length is a good choice. After some calculations/simulations, you will find the optimal size for NMOS & PMOS.

Hope it helps

regards,
jordan76

 

[cretu]

Re: The standard MUX size.

Hi twolevel2002,

If my understanding is correct, you need a CMOS switch for your comparator.
In this case the key point is to make sure there is low distortion and acceptable delay. As a rule of thumb, equal size with minimum length is a good choice. After some calculations/simulations, you will find the optimal size for NMOS & PMOS.

Hope it helps

regards,
jordan76

From real life experience, if you want to have close to equal rise and fall times, the ratio is from 2:1 to 3:1 in favour of the pmos. Which means at the same L the W of the PMOS should be between 2 and 3 times biger than the NMOS

 

[lastdance]

Re: The standard MUX size.

i believe you will not drive significant loads with your mux, in which case, if i were u, i would use the minimum size permitted in your process for both n and p in the mux to allow higher integration.

 

[cretu]

Re: The standard MUX size.

i believe you will not drive significant loads with your mux, in which case, if i were u, i would use the minimum size permitted in your process for both n and p in the mux to allow higher integration.

that's true. You'll have to use something else after it. My point was only for a regular inverter type. Anyway, I am not sure what exactly the application is in his case

Added after 1 minutes:

also depends if it is analog or digital mux (i guess it's digital)

 

[nitu]

Re: The standard MUX size.

Refer Logical Effort by David Harris .. Excellent book... For calculating sizes of gates for any design