Static information storage and retrieval – Floating gate
Patent
1999-05-10
2000-10-31
Elms, Richard
Static information storage and retrieval
Floating gate
36518521, 257239, 257258, G11C 1604
Patent
active
061412430
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monolithic integrated sensor element comprising a field effect transistor which is sensitive to a physical quantity to be detected and a non-volatile memory.
2. Description of the Prior Art
It is known to realize a sensor element and a non-volatile memory by two separate components on a chip. In so doing, e.g. an MOS transistor can act as a sensor and a second MOS transistor can act as a non-volatile memory. Known non-volatile memories of this type are EPROMs, Flash EPROMs, EEPROMs, etc. EEPROMs are frequently used as non-volatile memories in view of their simple programming. An analog storage of information in a single EEPROM cell can increase the storage density and simplify the circuit technologies for analog signal processing when long-term storage is required.
Since in the above-mentioned sensor elements according to the prior art the actual sensor and the non- volatile memory are realized by two transistors, a large chip area is necessary for realizing a sensor element. In addition, due to local parameter variations resulting from the manufacturing process, adaptation problems occur between the two transistors forming a sensor element, whereby a change in the output signal is caused. Furthermore, a signal processing unit is required which processes the sensor signal and the memory contents.
U.S. Pat. No. 4,788,581 relates to an MOS dosimeter used for measuring a dose within a radiation field. The dosimeter comprises a semiconductor substrate, an insulating layer on the semiconductor substrate, the insulating layer being resistant to the radiation and provided with a floating gate. In addition, a metal contact is connected to a semiconductor substrate. The floating gate is used for accumulating a charge, the accumulated charge corresponding to the dose of radiation. The accumulated charge can be reset for using the dosimeter once more.
JP-A-07115182 relates to a photoelectric transducer with a storage function in the case of which a silicon substrate has a layer provided therein into which a source layer and a drain layer have been diffused. A floating gate is arranged on a tunnel oxide film and, in addition, a control gate consisting of polycrystalline silicon is deposited on the floating gate, an oxide film being arranged between these two gates. A photoelectric transducer is formed by the photoconductive layer and a transparent electrode.
Thus there is a need to provide a space-saving sensor element with an associated non-volatile memory, the sensor element avoiding also adaptation problems between the sensor cell and the memory cell caused by local parameter variations resulting from the manufacturing process.
SUMMARY OF THE INVENTION
The present invention is a sensor device having a sensor element in the form of a field effect transistor sensitive to a physical quantity to be detected. The gate electrode of the field effect transistor is implemented as a floating gate. The floating gate is coupled to a programming unit by means of which charges are applied to and removed from the floating gate.
Due to the fact that the gate electrode of the transistor is implemented as a floating gate, the gate electrode can be used for adjusting the operating point of the transistor as well as for storing a charge corresponding to a physical quantity detected by the field effect transistor. For this purpose, the field effect transistor is circuited to a comparator and a propramming unit for the EEPROM, which is defined by the floating gate.
The non-volatile memory defined by the floating gate of the sensor element according to the present invention can be used for adjusting the operating point of the field effect transistor sensitive to a physical quantity to be detected, for storing coefficients for further signal processing, or for storing the detected signal itself. In accordance with a preferred embodiment of the present invention, the field effect transistor sensitive to a physical quantity to be detected is a photo
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Aslam Amer
Brockherde Werner
Hosticka Bedrich
Schanz Michael
Elms Richard
Fraunhofer-Gesellschaft zur Forderung der ange-wandten Forschung
Nguyen Hien
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