Please tell me what will be the block diagram of a 16:1 MUX using two 8:1 MUX!!....

 

Is this homework?

It is very simple.

You cannot use two muxes however.

You must use two 8:1 muxes and one 2:1 mux.

The 8:1 muxes select channel 0-15 and produce two outputs.

You then select the right mux using the 2:1 mux.

If you must use 8:1 muxes then with the last mux only two channels are used and only one select bit is used.

Actually there may be a way to use two 8:1 muxes, if they have a chip select. However, you will need to implement external logic to select the first or second mux.

 

It can't be done using two 8-input multiplexers alone. Depending on the type of 8-input multiplexer, some other logic will also be needed.

The circuit attached shows how two multiplexers with "3-state" outputs (that can be made open-circuit using an enable input) can be combined using an additional inverter.

The output goes open-circuit when the /EN input is high.