Analog neuromorphic circuit implemented using resistive memories

• US 10,474,948 B2
• Filed: 03/28/2016
• Issued: 11/12/2019
• Est. Priority Date: 03/27/2015
• Status: Active Grant

• Current Assignee: University of Dayton
• Original Assignee: University of Dayton
• Inventors: Yakopcic, Chris, Hasan, Raqibul, Taha, Tarek M.
• Primary Examiner(s): Nguyen, Hien N
• Application Number:
  US15/082,537
• Publication Number:
  US 20160284400A1
• Time in Patent Office: 1,324 Days
• CPC Class Codes: G06N 3/065 Analogue means
• CPC Class Codes: G11C 11/54 using elements simulating biological cells, e.g. neuron
• CPC Class Codes: G11C 13/0002 using resistive RAM [RRAM] elements

Abstract

An analog neuromorphic circuit is disclosed, having input voltages applied to a plurality of inputs of the analog neuromorphic circuit. The circuit also includes a plurality of resistive memories that provide a resistance to each input voltage applied to each of the inputs so that each input voltage is multiplied in parallel by the corresponding resistance of each corresponding resistive memory to generate a corresponding current for each input voltage and each corresponding current is added in parallel. The circuit also includes at least one output signal that is generated from each of the input voltages multiplied in parallel with each of the corresponding currents for each of the input voltages added in parallel. The multiplying of each input voltage with each corresponding resistance is executed simultaneously with adding each corresponding current for each input voltage.

Claims

1. An analog neuromorphic circuit that implements a plurality of resistive memories, comprising:

a plurality of input voltages applied to a plurality of inputs of the analog neuromorphic circuit with each input voltage applied to a corresponding horizontal wire from a plurality of horizontal wires;

a plurality of resistive memories with each resistive memory positioned at an intersection of the corresponding horizontal wire from the plurality of horizontal wires and a corresponding vertical wire from a pair of vertical wires with each horizontal wire interesting a first vertical wire and a second vertical wire from the pair of vertical wires forming a crossbar configuration and configured to;

provide a conductance to each input voltage applied to each of the inputs of each corresponding wire so that each input voltage is multiplied in parallel by the corresponding conductance of each corresponding resistive memory, and

generate a corresponding current as each conductance of each corresponding resistive memory is applied to each input voltage so that each corresponding current is added in parallel as each corresponding current propagates along the first vertical wire and the second vertical wire simultaneously with each multiplication of each input voltage by each corresponding conductance of each resistive memory;

a bias voltage is applied to a first accumulative current that is conducted by the first vertical wire to generate a first voltage value that is associated with the first accumulative current and to a second accumulative current that is conducted by the second vertical wire to generate a second voltage value that is associated with the second accumulative current;

a comparator coupled to the first vertical wire at a first input and to the second vertical wire at a second input and configured to compare the first voltage value associated with the first accumulative current that is conducted by the first vertical wire and the second voltage value associated with the second accumulative current that is conducted by the second vertical wire, wherein a first conductance of the resistive memories positioned on the first vertical wire and a second conductance of the resistive memories positioned on the second vertical wire are adjusted relative to each other based on the first voltage value and the second voltage value to obtain a functionality of the analog neuromorphic circuit; and

an output signal that is configured to execute the functionality of the analog neuromorphic circuit that is generated from each of the input voltages multiplied in parallel with each of the corresponding currents for each of the input voltages added in parallel and the adjusted first conductance and second conductance.

2. The analog neuromorphic circuit of claim 1, further comprising:

a plurality of horizontal wires positioned to intersect with a first pair of vertical wires forming a first wire grid so that each horizontal wire forms a row of the first wire grid and each vertical wire from the first pair of vertical wires forms a column of the first wire grid;

a first plurality of resistive memories with each resistive memory positioned at an intersection of the plurality of horizontal wires and the first pair of vertical wires and configured to;

provide a conductance to each input voltage applied to each horizontal wire so that each input voltage of the first wire grid is multiplied by the corresponding conductance to generate a current relative to each row of the first wire grid that is conducted by a first vertical wire of the first pair of vertical wires and by a second vertical wire of the first pair of vertical wires,

add each current relative to each row of the first wire grid to generate a first accumulative current of the first wire grid that is conducted by the first vertical wire of the first pair of vertical wires and a second accumulative current of the first wire grid that is conducted by the second vertical wire of the first pair of vertical wires; and

a first comparator coupled to the first vertical wire of the first pair of vertical wires at a first input and to the second vertical wire of the first pair of vertical wires at a second input and configured to;

compare a first voltage associated with the first accumulative current of the first wire grid to a second voltage associated with the second accumulative current of the first wire grid, and

generate a first output signal when the first voltage is greater than the second voltage and a second output signal when the second voltage is greater than the first voltage.

3. The analog neuromorphic circuit of claim 2, wherein the bias voltage is applied to a bias horizontal wire that is positioned between a last horizontal wire that has an input voltage from the plurality of input voltages applied and the first input and the second input of the first comparator to generate the first voltage value associated with the first accumulative current that is conducted by the first vertical wire and to generate the second voltage value associated with the second accumulative current that is conducted by the second vertical wire.

4. The analog neuromorphic circuit of claim 2, wherein the first comparator is further configured to generate a high voltage signal as the first output signal when the first voltage is greater than the second voltage and a low voltage signal as the second output signal when the second voltage is greater than the first voltage.

5. The analog neuromorphic circuit of claim 2, wherein each conductance provided by each resistive memory is weighted to determine a functionality of the analog neuromorphic circuit thereby triggering a change in the functionality of the analog neuromorphic circuit when each corresponding weight of each resistive memory is adjusted.

6. The analog neuromorphic circuit of claim 2, further comprising:

a second pair of vertical wires positioned to intersect relative to the plurality of horizontal wires forming a second wire grid;

a second plurality of resistive memories with each resistive memory positioned at an intersection of the plurality of horizontal wires and the second pair of vertical wires and configured to;

provide a resistance to each input voltage applied to each horizontal wire so that a multiplication of each input voltage of the second wire grid with the corresponding resistance is in parallel with a multiplication of each input voltage with the corresponding resistance of the first wire grid, and

add each current relative to each row of the second wire grid to generate a first accumulative current that is conducted by a first vertical wire of the second pair of vertical wires and a second accumulative current that is conducted by a second vertical wire of the second pair of vertical wires that is in parallel with the adding of the first wire grid; and

a second comparator coupled to the first vertical wire of the second pair of vertical wires at a first input of the second comparator and to the second vertical wire of the second pair at a second input of the second comparator and configured to;

compare a first voltage associated with the first accumulative current of the second wire grid to a second voltage associated with the second accumulative current of the second wire grid, and

generate a first output signal when the first voltage of the second wire grid is greater than the second voltage of the second wire grid and generate a second output signal when the second voltage of the second wire grid is greater than the first voltage of the second wire grid.

7. The analog neuromorphic circuit of claim 6, wherein each input voltage applied to each horizontal wire drives both the first wire grid and the first comparator forming a first neuron and the second wire grid and the second comparator forming a second neuron.

8. The analog neuromorphic circuit of claim 1, further comprising:

a plurality of bias voltages is applied to a corresponding bias horizontal wire from a plurality of bias horizontal wires that is positioned between the last horizontal wire that has the input voltage from the plurality of input voltages applied and the first input and the second input of the first comparator to generate the first voltage value associated with the first accumulative current that is conducted by the first vertical wire and the second voltage value associated with the second accumulative current that is conducted by the second vertical wire.

9. The analog neuromorphic circuit of claim 3, further comprising:

a bias voltage is applied to the bias horizontal wire that is positioned between the last horizontal wire that has the input voltage from the plurality of input voltages applied and the first input and the second input of the first comparator;

a first biasing resistive memory is positioned at an intersection of the bias horizontal wire and the first vertical wire and configured to provide a conductance to the bias voltage applied to the bias horizontal wire so that the bias voltage converts the first accumulated current conducted by the first vertical wire to the first voltage value; and

a second biasing resistive memory is positioned at an intersection of the bias horizontal wire and the second vertical wire and configured to provide a conductance to the bias voltage applied to the bias horizontal wire so that the bias voltage converts the second accumulated current conducted by the second vertical wire to the second voltage value.

10. The analog neuromorphic circuit of claim 5, further comprising:

a plurality of first weights associated with a first combination of resistive memories is adjusted to generate a negative value for the first combination of resistive memories, wherein the first plurality of first weights is applied to each corresponding conductance of the first combination of resistive memories thereby triggering a change in the functionality of the analog neuromorphic circuit when the plurality of first weights associated with the first combination of resistive memories is adjusted to generate the negative value for the first combination of resistive memories; and

a plurality of second weights associated with a second combination of resistive memories is adjusted to generate a positive value applied to each corresponding conductance of the second combination of resistive memories thereby triggering a change in the functionality of the analog neuromorphic circuit when the plurality of second weights associated with the second combination of resistive memories is adjusted to generate the positive value for the second combination of resistive memories.

11. A method for generating computation operations in parallel by implementing a plurality of resistive memories, comprising:

applying a plurality of input voltages to a plurality of inputs of an analog neuromorphic circuit with each input voltage applied to a corresponding horizontal wire from a plurality of horizontal wires;

providing, by a plurality of resistive memories, a conductance to each input voltage applied to each of the inputs of each corresponding wire so that each input voltage is multiplied in parallel by the corresponding conductance of each corresponding resistive memory, wherein each resistive memory is positioned at an intersection of the corresponding horizontal wire from the plurality of horizontal wires and a corresponding vertical wire from a pair of vertical wires with each horizontal wire intersecting a first vertical wire and a second vertical wire from the pair of vertical wires forming a crossbar configuration;

generating a corresponding current for each input voltage as each conductance of each corresponding resistive memory is applied to each input voltage so that each corresponding current is added in parallel as each corresponding current propagates along the first vertical wire and the second vertical wire simultaneously with each multiplication of each input voltage by each corresponding conductance of each resistive memory;

applying a bias voltage to a first accumulative current that is conducted by the first vertical wire to generate a first voltage value that is associated with the first accumulative current and to a second accumulative current that is conducted by the second vertical wire to generate a second voltage value that is associated with the second accumulative current;

comparing, by a comparator coupled to the first vertical wire at a first input and to the second vertical wire at a second input, the first voltage value associated with the first accumulative current that is conducted by the first vertical wire and the second voltage value associated with the second accumulative current that is conducted by the second vertical wire, wherein a first conductance of the resistive memories positioned on the first vertical wire and a second conductance of the resistive memories positioned on the second vertical wire are adjusted relative to each other based on the first voltage value and the second voltage value to obtain a functionality of the analog neuromorphic circuit; and

generating an output signal from each of the input voltages multiplied in parallel with each of the corresponding currents for each of the input voltages added in parallel and the adjusted first conductance and second conductance, wherein the functionality of the analog neuromorphic circuit is executed based on the output signal.

12. The method of claim 11, further comprising:

applying an input voltage to each horizontal wire positioned to intersect a first pair of vertical wires forming a first wire grid so that that each horizontal wire forms a row of the first wire grid and each vertical wire from the first pair of vertical wires forms a column of the first wire grid;

providing a conductance to each input voltage by a first plurality of resistive memories with each resistive memory positioned at an intersection of the plurality of horizontal wires and the first pair of vertical wires of the first wire grid;

multiplying each input voltage by the corresponding conductance to generate a current relative to each row of the first wire grid that is conducted by a first vertical wire of the first pair of vertical wires and by a second vertical wire of the first pair of vertical wires;

adding each current relative to each row of the first wire grid to generate a first accumulative current of the first wire grid that is conducted by the first vertical wire of the first pair of vertical wires and a second accumulative current of the first wire grid that is conducted by the second vertical wire of the first pair of vertical wires;

comparing a first voltage associated with the first accumulative current of the first wire grid to a second voltage associated with the second accumulative current of the first wire grid; and

generating a first output signal when the first voltage is greater than the second voltage and a second output signal when the second voltage is greater than the first voltage.

13. The method of claim 12, further comprising:

applying the bias voltage to a bias horizontal wire that is positioned between a last horizontal wire that has an input voltage from the plurality of input voltages applied and the first input and the second input of the first comparator;

generating the first voltage value associated with the first accumulative current that is conducted by the first vertical wire; and

generating the second voltage value associated with the second accumulative current that is conducted by the second vertical wire.

14. The method of claim 13, further comprising:

applying a bias voltage to the bias horizontal wire that is positioned between the last horizontal wire that has the input voltage from the plurality of input voltages applied and the first input and the second input of the first comparator;

providing a conductance to the bias voltage applied to the bias horizontal wire so that the bias voltage converts the first accumulated current conducted by the first vertical wire to the first voltage value by a first biasing resistive memory positioned at an intersection of the bias horizontal wire and the first vertical wire; and

providing a conductance to the bias voltage applied to the bias horizontal wire so that the bias voltage converts the second accumulated current conducted by the second vertical wire to the second voltage value by a second biasing resistive memory positioned at an intersection of the bias horizontal wire and the second vertical wire.

15. The method of claim 12, wherein the generating of the first output signal and the second output signal comprises:

generating a high voltage signal as the first output signal when the first voltage is greater than the second voltage; and

generating a low voltage signal as the second output signal when the second voltage is greater than the first voltage.

16. The method of claim 12, wherein each conductance provided by each resistive memory is weighted to determine a functionality of the analog neuromorphic circuit thereby triggering a change in the functionality of the analog neuromorphic circuit when each corresponding weight of each resistive memory is adjusted.

17. The method of claim 16, further comprising:

adjusting a plurality of first weights associated with a first combination of resistive memories to generate a negative value for the first combination of resistive memories, wherein the first plurality of first weights is applied to each corresponding conductance of the first combination of resistive memories thereby triggering a change in the functionality of the analog neuromorphic circuit when the plurality of first weights associated with the first combination of resistive memories is adjusted to generate the negative value for the first combination of resistive memories; and

adjusting a plurality of second weights associated with a second combination of resistive memories to generate a positive value applied to each corresponding conductance of the second combination of resistive memories thereby triggering a change in the functionality of the analog neuromorphic circuit when the plurality of second weights associated with the second combination of resistive memories is adjusted to generate the positive value for the second combination of resistive memories.

18. The method of claim 12, further comprising:

providing a resistance to each input voltage by a second plurality of resistive memories with each resistive memory positioned at an intersection of the plurality of horizontal wires and a second pair of vertical wires positioned to intersect the plurality of horizontal wires forming a second wire grid;

multiplying each input voltage of the second wire grid with the corresponding resistance in parallel with the multiplying of each input voltage with the corresponding resistance of the first wire grid;

adding each current relative to each row of the second wire grid to generate a first accumulative current that is conducted by the first vertical wire of the second pair of vertical wires and a second accumulative current that is conducted by a second vertical wire of the second pair of vertical wires that is in parallel with the adding of the first wire grid;

comparing a first voltage associated with the first accumulative current of the second wire grid to a second voltage associated with the second accumulative current of the second wire grid; and

generating a first output signal when the first voltage of the second wire grid is greater than the second voltage of the second wire grid and a second output signal when the second voltage of the second wire grid is greater than the first voltage of the second wire grid.

19. The method of claim 18, wherein the applying of the input voltage comprises:

applying each input voltage to each horizontal wire to drive both the first wire grid forming a first neuron and the second wire grid forming a second neuron.

20. The method of claim 11, further comprising:

applying a plurality of bias voltages to a corresponding bias horizontal wire from a plurality of bias horizontal wires that is positioned between the last horizontal wire that has the input voltage from the plurality of input voltages applied and the first and second input of the comparator; and

generating the first voltage value associated with the first accumulative current that is conducted by the first vertical wire and the second voltage value associated with the second accumulative current that is conducted by the second vertical wire.