US4434479A
Expired / Lapsed
US
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Nonvolatile memory sensing system
Assignee: McDonnell Douglas Corp
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Filing: 1981-11-02
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Granted: 1984-02-28
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Expires: 2001-11-02
Abstract
Abstract A sensing system for a nonvolatile memory transistor array employs reference transistors which are substantially identical to the memory transistors within the array and employs means to program the threshold voltage levels of the reference transistors to a lower level than that of the memory transistors within the array such that the changes in the electrical characteristics of both the memory and the reference transistors are proportional over time, the system thereby being rendered self-tracking.
Inventors
- 👤 Yung J. Chen
- 👤 Eden Y. C. Mei
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 03:51
CPC Classifications
G; G11; G11C; G11C16/00; G11C16/02; G11C16/06; G11C16/26; G11C16/28
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
88 words
In a memory system comprising a nonvolatile memory transistor array, a self-tracking sensing apparatus comprising: means to select a nonvolatile memory transistor to be sensed within the array; a reference nonvolatile transistor wherein the reference transistor is substantially identical to the memory transistors in the memory array; means to program the threshold voltage of the reference transistor to a lower level than that of an identically programmed memory transistors; and means to compare the programmed state of the memory transistor with the programmed state of the reference transistor.
Claim 2
Dependent Claim
88 words
In a memory system comprising a nonvolatile memory transistor array, a self-tracking sensing apparatus comprising: means to select a nonvolatile memory transistor to be sensed within the array; a reference nonvolatile transistor wherein the reference transistor is substantially identical to the memory transistors in the memory array; means to program the threshold voltage of the reference transistor to a lower level than that of an identically programmed memory transistors; and means to compare the programmed state of the memory transistor with the programmed state of the reference transistor.
Claim 3
Dependent Claim
12 words
The apparatus of claim 1 wherein the nonvolatile transistors are MNOS transistors.
Claim 4
Dependent Claim
13 words
The apparatus of claim 1 wherein the nonvolatile transistors are floating gate transistors.
Claim 5
Dependent Claim
22 words
The apparatus of claim 1 wherein the means to program the threshold voltage of the reference transistor comprises a voltage reduction circuit.
Claim 6
Dependent Claim
45 words
The apparatus of claim 1 wherein the means to program the threshold voltage of the reference transistor comprises a timing circuit which reduces the duration of the programming means in relation to the duration of the action of the programming means upon a memory transistor.
Claim 7
Dependent Claim
30 words
The apparatus of claim 1 wherein the means to compare the programmed state of the memory transistor with the programmed state of the reference transistor comprises a voltage sensing amplifier.
Claim 8
Dependent Claim
30 words
The apparatus of claim 1 wherein the means to compare the program state of the memory transistor with the programmed state of the reference transistor comprises a current sensing amplifier.
References Cited (Backward Citations)
US4376987A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-02-27 | 1987-08-29 | 1988-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-02-27 | 1991-08-29 | 1992-02-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-02-27 | 1995-08-29 | 1996-02-28 | $7700.00 | Window Closed / Lapsed |