The punchthrough device as a passive exponential load in fast static bipolar RAM cells

It is shown that the punchthrough device can be used as a passive exponential load in fast static bipolar RAM cells. The advantages are that the cell standby/read current ratio can be very large (> four decades), and that the cell area can be very small due to the fact that the punchthrough load is a vertical device. In this cell, a very small standby power dissipation(<0.1 μW) is combined with a short access time (<10 ns). A static noise margin calculation for the cell is included. The general standby/read switching behaviour of memory cells with exponential loads is explained. The cell sensitivity to α-particles is discussed.