I have some JFET's that I'm trying to put into a design of mine, but I'm curious about JFET symmetry. I am familiar with the JFET's basic operation, assuming I know which input is the source. In a symmetrical JFET what determines which pin is the source and which pin is the drain? The current direction through the JFET? In theory you can put the FET in circuit in either orientation, and it will continue to operate properly, meaning the source and drain can switch for some reason. What is that reason?