Storage device and driving method thereof
First Claim
1. A driving method of a storage device comprising a first memory cell and a second memory cell, wherein the first memory cell comprises a first transistor, a second transistor, and a first capacitor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, wherein the second memory cell comprises a third transistor, a fourth transistor, and a second capacitor, wherein one of a source and a drain of the third transistor is electrically connected to a second bit line, wherein the other of the source and the drain of the third transistor is electrically connected to a second source line, wherein one of a source and a drain of the fourth transistor is electrically connected to a gate of the third transistor, wherein the other of the source and the drain of the fourth transistor is electrically connected to the second bit line, and wherein a first electrode of the second capacitor is electrically connected to the gate of the third transistor, the driving method comprising the steps of:
- supplying a first potential to the first source line;
supplying a second potential to the first bit line;
electrically isolating the first bit line after supplying the second potential to the first bit line;
changing a potential of a second electrode of the first capacitor from a third potential to a fourth potential so that the first potential or the second potential is supplied to the first bit line;
supplying a fifth potential lower than the second potential to the second bit line;
supplying a sixth potential or a seventh potential to the first bit line in accordance with the potential of the first bit line; and
turning on a switch provided between the first bit line and an input-output line to read out data of the first bit line.
1 Assignment
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Accused Products
Abstract
An object is to provide a highly integrated storage device which can operate at high speed and a driving method thereof. The storage device includes two storage portions, two precharge switches, and one sense amplifier. In each of the storage portions, storage elements are arranged in a matrix. In each of the storage elements, a node electrically connected to a source or a drain of a transistor whose off-state current is small is a memory storing portion. A page buffer circuit is unnecessary; thus, high-speed operation is possible and high integration is achieved.
102 Citations
25 Claims
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1. A driving method of a storage device comprising a first memory cell and a second memory cell, wherein the first memory cell comprises a first transistor, a second transistor, and a first capacitor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, wherein the second memory cell comprises a third transistor, a fourth transistor, and a second capacitor, wherein one of a source and a drain of the third transistor is electrically connected to a second bit line, wherein the other of the source and the drain of the third transistor is electrically connected to a second source line, wherein one of a source and a drain of the fourth transistor is electrically connected to a gate of the third transistor, wherein the other of the source and the drain of the fourth transistor is electrically connected to the second bit line, and wherein a first electrode of the second capacitor is electrically connected to the gate of the third transistor, the driving method comprising the steps of:
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supplying a first potential to the first source line; supplying a second potential to the first bit line; electrically isolating the first bit line after supplying the second potential to the first bit line; changing a potential of a second electrode of the first capacitor from a third potential to a fourth potential so that the first potential or the second potential is supplied to the first bit line; supplying a fifth potential lower than the second potential to the second bit line; supplying a sixth potential or a seventh potential to the first bit line in accordance with the potential of the first bit line; and turning on a switch provided between the first bit line and an input-output line to read out data of the first bit line. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A driving method of a storage device comprising a first memory cell and a sense amplifier, wherein the first memory cell comprises a first transistor, a second transistor, and a first capacitor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, and wherein the first bit line is electrically connected to the sense amplifier, the driving method comprising the steps of:
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supplying a first potential to the first bit line; electrically isolating the first bit line after supplying the first potential to the first bit line; changing a potential of a second electrode of the first capacitor so that a signal is output to the first bit line in accordance with a voltage held in the first capacitor; amplifying the signal by the sense amplifier; and reading out the amplified signal through a switch from the first bit line to an input-output line by turning on the switch. - View Dependent Claims (8, 9, 10)
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11. A driving method of a storage device comprising a first memory cell and a second memory cell, wherein the first memory cell comprises a first transistor, a second transistor, and a first capacitor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, wherein the second memory cell comprises a third transistor, a fourth transistor, and a second capacitor, wherein one of a source and a drain of the third transistor is electrically connected to a second bit line, wherein the other of the source and the drain of the third transistor is electrically connected to a second source line, wherein one of a source and a drain of the fourth transistor is electrically connected to a gate of the third transistor, wherein the other of the source and the drain of the fourth transistor is electrically connected to the second bit line, and wherein a first electrode of the second capacitor is electrically connected to the gate of the third transistor, the driving method comprising the steps of:
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supplying a first potential to the first source line; supplying a second potential to the first bit line; electrically isolating the first bit line after supplying the second potential to the first bit line; changing a potential of a second electrode of the first capacitor from a third potential to a fourth potential so that the first potential or the second potential is supplied to the first bit line; supplying a fifth potential lower than the second potential to the second bit line; turning on a switch provided between the first bit line and an input-output line so that a sixth potential or a seventh potential is supplied to the first bit line, whereby data is written to the first memory cell; and turning off the second transistor after turning on the switch. - View Dependent Claims (12, 13, 14, 15, 16)
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17. A driving method of a storage device comprising a first memory cell, a second memory cell, and a sense amplifier, wherein the first memory cell comprises a first transistor, a second transistor, and a first capacitor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, wherein the first bit line is electrically connected to the sense amplifier, wherein the second memory cell comprises a third transistor, a fourth transistor, and a second capacitor, wherein one of a source and a drain of the third transistor is electrically connected to a second bit line, wherein the other of the source and the drain of the third transistor is electrically connected to a second source line, wherein one of a source and a drain of the fourth transistor is electrically connected to a gate of the third transistor, wherein the other of the source and the drain of the fourth transistor is electrically connected to the second bit line, wherein a first electrode of the second capacitor is electrically connected to the gate of the third transistor, and wherein the second bit line is electrically connected to the sense amplifier, the driving method comprising the steps of:
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turning on the second transistor; inputting a first signal through a first switch from a first input-output line to the first bit line by turning on the first switch; inputting a second signal through a second switch from a second input-output line to the second bit line by turning on the second switch; and turning off the second transistor after inputting the first signal and the second signal, wherein the first signal and the second signal are amplified by the sense amplifier. - View Dependent Claims (18, 19)
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20. A storage device comprising:
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a first storage portion; a second storage portion; a first switch, a second switch, a first driver circuit, and a second driver circuit, wherein in each of the first storage portion and the second storage portion, a plurality of storage elements is arranged in a matrix, wherein the first storage portion is electrically connected to the first switch, wherein the second storage portion is electrically connected to the second switch, wherein the first driver circuit comprises is two precharge switches and one sense amplifier, wherein in each of the plurality of storage elements, a node electrically connected to a source or a drain of a first transistor is a memory storing portion, and wherein the first transistor comprises a first channel formation region comprising an oxide semiconductor. - View Dependent Claims (21, 22)
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23. A storage device comprising:
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a first memory cell comprising; a first transistor; a second transistor; and a first capacitor; a second memory cell comprising; a third transistor; a fourth transistor; and a second capacitor; and a sense amplifier comprising; a fifth transistor; a sixth transistor; a seventh transistor; and an eighth transistor, wherein one of a source and a drain of the first transistor is electrically connected to a first bit line, wherein the other of the source and the drain of the first transistor is electrically connected to a first source line, wherein one of a source and a drain of the second transistor is electrically connected to a gate of the first transistor, wherein the other of the source and the drain of the second transistor is electrically connected to the first bit line, wherein a first electrode of the first capacitor is electrically connected to the gate of the first transistor, wherein the first bit line is electrically connected to the sense amplifier, wherein one of a source and a drain of the third transistor is electrically connected to a second bit line, wherein the other of the source and the drain of the third transistor is electrically connected to a second source line, wherein one of a source and a drain of the fourth transistor is electrically connected to a gate of the third transistor, wherein the other of the source and the drain of the fourth transistor is electrically connected to the second bit line, wherein a first electrode of the second capacitor is electrically connected to the gate of the third transistor, wherein the second bit line is electrically connected to the sense amplifier, wherein one of a source and a drain of the fifth transistor is electrically connected to the first bit line, wherein a gate of the fifth transistor is electrically connected to the second bit line, wherein one of a source and a drain of the sixth transistor is electrically connected to the first bit line, wherein a gate of the sixth transistor is electrically connected to the second bit line, wherein one of a source and a drain of the seventh transistor is electrically connected to the second bit line, wherein a gate of the seventh transistor is electrically connected to the first bit line, wherein one of a source and a drain of the eighth transistor is electrically connected to the second bit line, and wherein a gate of the eighth transistor is electrically connected to the first bit line. - View Dependent Claims (24, 25)
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Specification