Data sense apparatus for use in multi-threshold read only memory
First Claim
1. A read only memory comprising a plurality of multi-state cells interconnected in a ROM matrix, each of said cells comprising a FET, and the FET of each ROM cell having substantially the same surface area and shape, and having one of at least three possible states;
- means for selecting a particular one of said cells to be read;
means for applying to a selected cell, an input signal varying in amplitude with time for stimulating an output signal from said cell in accordance with the state of said cell, said output signal being of one at least two possible amplitude levels;
said input signal varies slowly with time, and said output signal being displaced in time depending upon the state of said cell.
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Accused Products
Abstract
A read only memory in which the memory cells are single metal gate or silicon gate field effect transistors. Each FET has one of several different thresholds or states. The size or area of the FET gates at the surface of the semiconductor chip are substantially the same regardless of the cells threshold or state. The input to the gates is a ramp, and the cells are rendered conducting by the amplitude of the ramp at a given instant. The output of a cell is fed to several flip-flops, which are synchronized with the input ramp, thereby setting the flip-flops in accordance with the threshold or state of the cell. An encoder converts the output from the flip-flops to a bit binary signal. This permits a very high density ROM, e.g. 128K on a single chip. In another embodiment the input to the gates is a step, and the cells are all rendered conducting simultaneously. The amount of current drawn by each gate however, depends upon the doping in the gate region. The amplitude of the current being drawn by a selected cell is compared with the reference , this in turn is decoded to indicate the state of that cell.
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Citations
11 Claims
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1. A read only memory comprising a plurality of multi-state cells interconnected in a ROM matrix, each of said cells comprising a FET, and the FET of each ROM cell having substantially the same surface area and shape, and having one of at least three possible states;
- means for selecting a particular one of said cells to be read;
means for applying to a selected cell, an input signal varying in amplitude with time for stimulating an output signal from said cell in accordance with the state of said cell, said output signal being of one at least two possible amplitude levels;
said input signal varies slowly with time, and said output signal being displaced in time depending upon the state of said cell. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- means for selecting a particular one of said cells to be read;
Specification