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US 5,331,597 AGranted
Semiconductor nonvolatile memory apparatus including threshold voltage shift circuitry
AssigneeKabushiki Kaisha Toshiba
InventorSumio Tanaka
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Abstract
A semiconductor nonvolatile memory apparatus is composed of differential cells in which data can be written electrically, data reading sense amplifiers for reading data from these cells, and threshold voltage shift checking sense amplifier connected to respective sense inputs of the sense amplifiers through selecting switching elements and checking threshold voltages of respective transistors within the differential type cells. According to this semiconductor nonvolatile memory apparatus, data can be read out at high speed without increasing the chip size.
Claims6
A semiconductor memory device, comprising:
- a differential memory cell for storing data and including a first transistor having a first threshold voltage and a second transistor having a second threshold voltage;
- a first bit line connected to said first transistor;
- a second bit line connected to said second transistor;
- a first column selecting transistor having a first terminal connected to said first bit line and a gate thereof receiving a column selection signal;
- a second column selecting transistor having a first terminal connected to said second bit line and a gate thereof receiving said column selection signal;
- a data reading sense amplifier for reading data from said memory cell and having a first input connected to a second terminal of said first column selecting transistor and a second input connected to a second terminal of said second column selecting transistor;
- threshold voltage shift detecting circuitry including first and second threshold voltage shift detecting sense amplifiers for detecting threshold voltage shifts of said first and second transistors, respectively;
- a first switching element connected in series between said first threshold voltage shift checking circuit and said first input of said data reading sense amplifier;
- and
- a second switching element connected in series between said threshold voltage shift checking circuit and said second input of said data reading sense amplifier.
7 more elements
Dependencies are inferred from the claim text.