A memory system includes an isolated first well of a first polarity and an array of volatile memory cells. Each of the memory cells includes a first set of transistors in the isolated first well, and a second set of transistors. A source bias circuit is coupled to the array of volatile memory cells. At least a portion of the source bias circuit is in the isolated first well and coupled to source electrodes of the first set of transistors of each of the memory cells. A control circuit is configured to enable the source bias circuit.