Neural network having an associative memory that learns by example
First Claim
1. A neural network comprising;
- a matrix of a plurality of output electrodes intersecting with a plurality of input electrodes at intersecting regions, and a plurality of electronic elements coupling said output electrodes to said input electrodes at said intersecting regions;
means interconnecting said electronic elements such that input signals are continuously processed by said electronic elements;
each of said electronic elements comprising an analog threshold device in which its output voltage increases substantially symmetrically in both the positive and negative directions from a threshold voltage as a function of its input voltage.
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Abstract
A neural network utilizing the threshold characteristics of a semiconductor device as the various memory elements of the network. Each memory element comprises a complementary pair of MOSFETs in which the threshold voltage is adjusted as a function of the input voltage to the element. The network is able to learn by example using a local learning algorithm. The network includes a series of output amplifiers in which the output is provided by the sum of the outputs of a series of learning elements coupled to the amplifier. The output of each learning element is the difference between the input signal to each learning element and an individual learning threshold at each input. The learning is accomplished by charge trapping in the insulator of each individual input MOSFET pair. The thresholds of each transistor automatically adjust to both the input and output voltages to learn the desired state. After input patterns have been learned by the network, the learning functions is set to zero so that the thresholds remain constant and the network will come to an equilibrium state under the influence of a test input pattern thereby providing, as an output, the learned pattern most closely resembling the test input pattern.
39 Citations
28 Claims
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1. A neural network comprising;
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a matrix of a plurality of output electrodes intersecting with a plurality of input electrodes at intersecting regions, and a plurality of electronic elements coupling said output electrodes to said input electrodes at said intersecting regions; means interconnecting said electronic elements such that input signals are continuously processed by said electronic elements; each of said electronic elements comprising an analog threshold device in which its output voltage increases substantially symmetrically in both the positive and negative directions from a threshold voltage as a function of its input voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A neural network suitable for information processing, comprising:
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means for outputting a plurality of network output voltages, each of said network output voltages being the sum of the outputs of a series of learning elements having an adjustable threshold value as a memory means, the input of each respective learning element being a respective one of said network output voltages; the output of each learning element being proportional to its input voltage minus a learned threshold value at its input, the output voltage having a functional relationship with respect to the input voltage which is symmetric and monotonically increasing about said threshold value; the threshold value being adjustable as a function of the input voltage of the learning element and its corresponding network output voltage in a learning mode, the functional relationship being of the form;
space="preserve" listing-type="equation">T.sub.ij.sup.* =T.sub.ij +α
(|V.sub.j -V.sub.i -β
)where, Tij* =the new threshold value; Tij =the former threshold value; α
=a learning rate constant;β
=a learning step;Vi =the ith network output voltage; Vj =the jth input voltage of the network; i=l to M; j=l to N; M=total number of output means; N=total number of input electrodes. means for selectively setting α
to zero so that the threshold value remains constant in an associative memory mode;whereby said neural network operates in said learning mode wherein in response to a pattern of desired output signals applied to the network, the threshold value of each learning element continually adjusts such that the threshold value of each element represents the learned states that will provide the desired output pattern in response to a given input pattern; and
said neural network operates in said associative memory mode wherein the threshold values remain constant and the output of each learning element reaches a steady state that is only dependent upon the input signals of a test input pattern such that the output voltages of the network provide the desired learned output pattern most closely related to the test input pattern. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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23. A memory element of an artificial neuron comprising:
- a complementary pair of field effect transistors connected in parallel, the gates of said pair being connected together to an input terminal, the drains of said pair being connected together to an output terminal and the sources of said pair being connected together to a fixed potential, the output voltage of said memory element increasing substantially symmetrically in both the positive and negative direction from a threshold voltage as a function of the input voltage of said memory element.
- View Dependent Claims (24, 25, 26, 27, 28)
Specification