Understanding analog multiplexer internal circuitry that contains extra MOSFETs

[avi9526]

I saw some basic examples of analog switches with 2 MOSFETs. But then I check internal circuitry of the 74HC4051 described in the datasheet and there was some extra MOSFETs. See attached picture. Purpose of logics and the first MOSFET from right is clear but other MOSFETs are mystery to me. Could someone help me with that please.

 

[stenzer]

Hi,

that should be the "break before make" implementation. Each inverter will add a delay, ensuring a faster turn-off of the switch by the NAND, while the NOR will turn on the switch later. Consider two of this switches getting controlled at the same time, one should be opened, the other one closed. The two switches shall never be connected to "Z" at the same time. The additional 3 MOSFETS are needed to realize this function.

You can make a simple simulation including the delay of the individual logic gates to display the behaviour.

BR