Swapped-body RAM architecture
A method for operating an SRAM cell comprises, during a read operation, forward biasing an N-well of a first and second pull-up transistor, and forward biasing a P-well of a first and second pull-down transistor and a first and second access transistor. The method further comprises, during a write operation, zero or reverse biasing an N-well of a first and second pull-up transistor, and forward biasing a P-well of a first and second pull-down transistor and a first and second access transistor. The method further comprises, during an idle state, zero biasing an N-well of a first and second pull-up transistor and zero biasing a P-well of a first and second pull-down transistor and a first and second access transistor. In addition, one or more rows or columns of memory cells may receive a bias voltage.
1. A memory cell, comprising:
first and second access transistors, wherein the first access transistor is connected to a word line and connected between a first bit line and a first data node, and wherein the second access transistor is connected to the word line and connected between a second bit line and a second data node;
first and second pull-up transistors, wherein the first pull-up transistor is connected to a first power supply point and to the first data node, and wherein the second pull-up transistor is connected to the first power supply point and the second data node;
first and second pull-down transistors, wherein the first pull-down transistor is connected to a second power supply point and to the first data node, and wherein the second pull-down transistor is connected to the second power supply point and to the second data node;
wherein the memory cell can perform a read operation, a write operation, or reside in an idle state;
wherein during a read operation the first and second pull-up transistors, the first and second pull-down transistors, and the first and second access transistors receive a forward bias voltage; and
wherein during a write operation the first and second pull-up transistors receive a zero or reverse bias voltage, wherein receiving a zero or reverse bias voltage at the first and second pull-up transistors comprises zero or reverse biasing a well region of the first and second pull-up transistors to a voltage at the first power supply point and wherein the first and second pull-down transistors and the first and second access transistors receive a forward bias voltage.
2. The cell of claim 1 , wherein when residing in an idle state the first and second pull-up transistors, the first and second pull-down transistors, and the first and second access transistors receive a zero bias voltage.
3. The cell of claim 1 , wherein the first and second pull-up transistors are P-type devices residing in an N-well.
4. The cell of claim 3 , wherein receiving a forward bias voltage at the first and second pull-up transistors comprises forward biasing the N-well of the first and second pull-up transistors to a voltage at the second power supply point.
5. The cell of claim 4 , wherein biasing the N-well comprises biasing one or more rows or columns of memory cells.
6. The cell of claim 1 , wherein the first and second pull-down transistors and the first and second access transistors are N-type devices residing in a P-well, the P-well further residing in an N-well.
7. The cell of claim 6 , wherein receiving a forward bias voltage at the first and second pull-down transistors and the first and second access transistors comprises forward biasing the P-well of the first and second pull-down transistors and the first and second access transistors to a voltage at the first power supply point.
8. The cell of claim 7 , wherein biasing the P-well comprises biasing one or more rows or columns of memory cells.
9. The cell of claim 2 , wherein receiving a zero bias voltage at the first and second pull-down transistors and the first and second access transistors comprises zero-biasing a P-well of the first and second pull-down transistors and the first and second access transistors to a voltage at the second power supply point.
10. The cell of claim 1 , wherein the second power supply point is zero volts.
11. The cell of claim 1 , wherein the first power supply point is 0.5 volts.
12. The cell of claim 1 , wherein the first and second pull-up transistors, the first and second pull-down transistors, and the first and second access transistors comprise JFET devices.
13. The cell of claim 12 , wherein a threshold voltage of the JFET devices is between 0.2 volts and −0.2 volts when forward biased.
14. The cell of claim 6 , wherein the P-well is connected to the word line.