Methods and systems of neuron leaky integrate and fire circuits

Patent metadata

Field	Value
Publication number	US-10643125-B2
Application number	US-201615059738-A
Country	US
Kind code	B2
Filing date	Mar 3, 2016
Priority date	Mar 3, 2016
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

Embodiments include methods and systems of neuron leaky integrate and fire circuit (NLIFC). Aspects include: receiving an input current having both AC component and DC component at an input terminal of the NLIFC, extracting AC component of input current, generating a number of swing voltages at a swing node using extracted AC component of the input current, transferring charge from a pull-up node to a neuron membrane potential (NP) node through an integration diode and a pull-up diode to raise a voltage at NP node over an integration capacitor gradually and the voltage at NP node shows integration value of AC component of input current, implementing leaky decay function of the neuron leaky integrate and fire circuit, detecting a timing of neuron fire using an analog comparator, resetting a neuron membrane potential level for a refractory period after neuron fire, and generating fire output signal of the NLIFC.

First claim

What is claimed is:

1. A neuron leaky integrate and fire circuit comprising:
an input additional gain stage;
an integration circuit having an input capacitor, an integration diode, and an integration capacitor electrically coupled in serial, wherein a first terminal of the input capacitor is electrically coupled to an output node of the additional gain stage voltage, a second terminal of the input capacitor is electrically coupled to an anode of the integration diode to form a swing node, a cathode of the integration diode is electrically coupled to a first terminal of the integration capacitor to form a neuron membrane potential node, and a second terminal of the integration capacitor is electrically coupled to a ground;
a pull-up circuit having a pull-up diode, wherein an anode of the pull-up diode is electrically coupled to a pull-up input terminal, and a cathode of the pull-up diode is electrically coupled to the swing node;
a leak control circuit having a leak control FET, wherein a gate of the leak control FET is electrically coupled to a leak control input terminal, a drain of the leak control FET is electrically coupled to the neuron membrane potential node, and a source of the leak control FET is electrically coupled to ground;
an analog comparator having a positive input terminal electrically coupled to the neuron membrane potential node, and a negative input terminal electrically coupled to an input terminal which supplies threshold level of neuron fire;
a reset circuit having a reset FET, wherein a gate of the reset FET is electrically coupled to a reset control circuit, a drain of the reset FET is electrically coupled to the neuron membrane potential node, and a source of the reset FET is electrically fixed to reset level or ground level; and
a rise edge detector having an input electrically coupled to an output terminal of the analog comparator, and an output terminal electrically coupled to a neuron fire output terminal of the neuron leaky integrate and fire circuit, wherein the rise edge detector is configured to generate fire pulse by sending out the pulse at the fire output terminal of the neuron leaky integrate and fire circuit when the rise edge detector detects a rise edge of a signal at the output of the analog comparator,
wherein the input additional gain stage comprises an operational amplifier, a first resistor, and a second resistor, wherein the input terminal of the neuron leaky integrate and fire circuit is electrically coupled to a positive input of the input operational amplifier, a first terminal of the first resistor is electrically coupled to a bias input terminal, a second terminal of the first resistor is electrically coupled to a negative input of the operational amplifier and a first terminal of the second resistor, and a second terminal of the second resistor is electrically coupled to an output of the operational amplifier and the input side node of the input capacitor.

2. A method of removing input AC current from a neuron leaky integrate and fire circuit comprising:
receiving an input current having both AC component and DC component at an input terminal of the neuron leaky integrate and fire circuit;
extracting the AC component of the input current by using an input capacitor;
generating a plurality of swing voltages at a swing node using the extracted AC component of the input current;
transferring charge from a pull-up node to a neuron membrane potential node through an integration diode and a pull-up diode to raise a voltage at the neuron membrane potential node over an integration capacitor gradually, wherein the voltage at the neuron membrane potential node shows the integration value of AC component of the input current;
implementing leaky decay function of the neuron leaky integrate and fire circuit using a leak current of a leak control FET of a leak control circuit;
detecting a timing of neuron fire using an analog comparator;
resetting a neuron membrane potential level for a refractory period after a neuron fire; and
generating fire output signal of the neuron leaky integrate and fire circuit;
wherein the neuron leaky integrate and fire circuit further comprises an input additional gain stage having an operational amplifier, a first resistor, and a second resistor, wherein the input terminal of the neuron leaky integrate and fire circuit is electrically coupled to a positive input of the operational amplifier, a first terminal of the first resistor is electrically coupled to a bias input terminal, a second terminal of the first resistor is electrically coupled to a negative input of the operational amplifier and a first terminal of the second resistor, and a second terminal of the second resistor is electrically coupled to an output terminal of the operational amplifier and the input capacitor.

3. The method of claim 2 , wherein the neuron leaky integrate and fire circuit comprises:
the integration circuit having the input capacitor, the integration diode, and the integration capacitor electrically coupled in serial, wherein a first terminal of the input capacitor is electrically coupled to an input voltage, a second terminal of the input capacitor is electrically coupled to an anode of the integration diode to form the swing node, a cathode of the integration diode is electrically coupled to a first terminal of the integration capacitor to form the neuron membrane potential node, and a second terminal of the integration capacitor is electrically coupled to a ground;
a pull-up circuit having the pull-up diode, wherein an anode of the pull-up diode is electrically coupled to the pull-up input terminal, and a cathode of the pull-up diode is electrically coupled to the swing node;
the leak control circuit having a leak control FET, wherein a gate of the leak control FET is electrically coupled to a leak control input terminal, a drain of the leak control FET is electrically coupled to the neuron membrane potential node, and a source of the leak control FET is electrically coupled to ground;
an analog comparator having a positive input terminal electrically coupled to the neuron membrane potential node, and a negative input terminal electrically coupled to an input terminal which supplies a threshold level of neuron fire;
a reset circuit having a reset FET, wherein a gate of the reset FET is electrically coupled to a reset control circuit, a drain of the reset FET is electrically coupled to the neuron membrane potential node, and a source of the reset FET is electrically fixed to the reset level or ground level; and
a rise edge detector having an input electrically coupled to an output terminal of the analog comparator, and an output terminal electrically coupled to a fire output terminal of the neuron leaky integrate and fire circuit, wherein the rise edge detector is configured to generate fire pulse by sending out the pulse at the fire output terminal of the neuron leaky integrate and fire circuit when the rise edge detector detects a rise edge of a signal at the output of the analog comparator.

4. The method of claim 2 , wherein the input capacitor is configured to cut off DC component of an input current and extract AC component of the input current, wherein a leaky decay function by a leaky current through the leak control FET is implemented on the neuron membrane potential node without the effect of large DC component and fluctuation of the input current at the input terminal of the neuron leaky integrate and fire circuit.

5. The method of claim 2 , wherein the analog comparator is configured to compare the voltage at the neuron membrane potential node with the threshold level of neuron fire, wherein when the voltage at the neuron membrane potential node is equal to the threshold level of neuron fire, the voltage at the neuron membrane potential node

Assignees

• IBM

Inventors

• Ritter Mark B
• Yasuda Takeo

Classifications

• G06N3/049 Primary

  Temporal neural networks, e.g. delay elements, oscillating neurons or pulsed inputs · CPC title

• G06N3/0635 Primary

  Physics · mapped topic

• G06N3/065 Primary

  Analogue means · CPC title