I am trying to design a set of switches in a cmos design.
The switches are supposed to control a number of capacitors and I want to implement them as single NMOS or PMOS transistors.
Based on my understanding I have done the following: Choosing PMOS for switches where the voltage signals switched are closest to VDD and NMOS for switching voltages closer to gnd, to enable optimal drive conditions and this way decrease Rds_on. All the switches are driven rail-to-rail.
I also think that I have to ensure that all the switches operate in the ohmic region.
But when it comes to wiring the body terminals I get a little bit confused. I have read that you should tie the body terminal to the source terminal/gnd in the case of NMOS. In my design, some of the switches are placed in between a PMOS sitting at the top and NMOS. In this case the source terminal is not connected to the lowest potential, should it then be wired to ground or the source terminal?
I have also heard that transistors in common design processes are symmetric devices. Does this mean that it does not matter if the drain and source terminal are swapped? Does the body potential influence this polarity?