Hi, does anyone know how to design a switch so that it passes both positive and negative voltage? If I use NMOS switch or the CMOS transmission gate, the lowest voltage can be passed is -Vthn, which is the threshold voltage for NMOS. So far, I know the PMOS switch would work. But the switch I am trying to design has to connect to one of the two power supplies. So, if the PMOS switch connects to the negative power supply, then it can pass the negative voltage. However, when it connects to the positive power supply, it doesnt pass the positive voltage. I have attached a file that shows the switch that I am suppose to design. The positive power supply is Vref and the negative power supply is -Vin.