SRAM
Suppose the drain of M1 is called point A; the drain of M5 is called point B.
Read: Both bitlines start at Vdd (Precharged), cell pulls one down;
Suppose now A=VDD, B=GND;
M1 and M4 are cut off;
1) M2 and M3 are both pulling up, there would be no sizing constrains;
2) M5 is in triode and is pulling down, M6 is in saturation and is pulling up;
3) M5 must win to avoid flipping the cell.
Write: One bitline is pulled low, low bitline value overpowers cell;
Suppose still now A=VDD, B=GND; bitline is pulled down to GND, bitline_bar stays at high
M1 and M4 are cut off;
(1) Write a low: M2 and M3 are both in triode, M2 must overwrite M4;
(2) Write a hight: M5 is in triode, M6 is in saturation, M6 must overwrite M1, this condition is contradict with the condition in READ mode.
DRAM
