Help on analog signal multiplexer

Hi all,I'm doing design on CIS pixel.
Now I'm going to tapout about half dozen of pixels with different types.So I have also design a analog signal multiplexer to select one of them and read the output signal,but i don't know much about this circuitry design,how can I implement a simple but usable one for my purpose?Any comments and material will be helpful!!
PLS give me most detailed instruction,I'm really new to this kind of design...


PS:My idea is:for 8 pixels,design a multiplexer takes 3 binary input(for my case,just use 3 dip switch on pcb and connect them to pins on test chip) and select one of the 8 pixels to be readable.For example input 010 to select to read the second pixel...

THX in advance

well mosfets are generally used in analog MUX.... you adjust the gate voltage deep enough that the mosfets you want are off and you give the necessary gate voltage only to the mosfet in the path which you want to be connected.....

to make the MUX bidirectional in terms of current flow.... an NMOS and PMOS are connected with their sources and drains connected together and their gates controlled using directed signal for one and inverted signal for the other.....

Thanks anand!
My signal flow is single directional,so i will try nmos/pmos transmission gate.

How about the 3to8 decoder?It should read input signal like 001 and give output high(low) enough to on(off) the correspond mos switch

ya that is the basic idea.... you got to use digital logic with the logic levels of the gates being much larger than the range of your input signal so that the mos stays in saturation region......

I think I should make switch in triode region...For saturation mos,it cannot be used as switch

i meant that the mosfet which is on must be in the saturation region and those mosfet which are off must be in the cutoff region....

A.Anand Srinivasan said:

i meant that the mosfet which is on must be in the saturation region and those mosfet which are off must be in the cutoff region....

Click to expand...

NO,I don't think so,for classic 3T pixel,one source follower mos is in saturation,but for the row select mos(just like my analog switch mos here)is in triode(linear) region.Of course when I don't wanna read out this pixel,the row select mos should be off...

well you are talking about the mosfet which selects and i'm talking about the mosfet which acts as a connection between the input and the output......

no,when I mean select mos,I mean mos in linear region connect between the source of source follower and output,check the pic out.

Maybe you are talking about mos generating controlling signal on the select mos' gate?That should be the 3to8 decoder stuff I'm worrying about.But I think with a VDD-GND level logic output,the select mos should effectively in linear or off region for my analog signal switching purpose

Anyway,where can I find stuff on how to build a 3 to 8 decoder logic?

what i was talking about was the source follower which passes the input to the output and the mos select you are talking about just acts as an fuse.... here these are constantly being scanned and hence the source followers is always kept on and when needed the mos select is switched on i.e. made to act as resistor and the power is obtained......

in the analog mux i was talking about the mos select's output is given to the gate of the mos between the input and output and only the mos in the selected path is on...
refer this link to understand what i'm trying to say
https://books.google.com/books?id=b...g+multiplexer&sig=IJJYy2IJZ2wzKO_qtPBF7C11YKA

Added after 4 minutes:

about the 3 to 8 decoder you are talking about.... we did some reading and couldn't find much material and all that we could get was this basic idea and explanation of what it does..... i couldn't find any circuit or layout in any of the books....

we tried a bidirectional one using discrete components and it didnt work because we couldn't match the mos....

I meant this...check it out

PS:All video out is connect to one PIN,so I can read out on the same pin and just switch between pixels.

k.... you have mentioned that you want to make a 3 to 8 decoder... i dont understand what you meant by that... because a 3 to 8 decoder just turns on a single pin based on the 3 bit input...

you have been talking about analog all along so only i'm confused...