Synapse Array Inverting Circuits for Smooth Sigmoid Outputs
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Solution Overview
Problem
Neuromorphic devices face challenges in achieving smooth output signals, which are crucial for mimicking brain-like functionality, as existing devices often produce abrupt changes in output voltage resembling pulse or step functions rather than the desired sigmoidal shape.
Innovation Solution
The neuromorphic device incorporates inverting circuits with specific configurations, including series-connected PMOS and NMOS transistors, and integrators with comparators, to smooth pulse-shaped input and output signals, ensuring the output resembles a sigmoid function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional neuromorphic devices use simple output circuits, then device complexity is reduced, but the output signal becomes abrupt (pulse or step function) rather than smooth (sigmoid shape)
Solution Approach 1:
The patent introduces an inverting circuit as an intermediary component between the synapse array and the output. This inverting circuit includes a pull-up transistor and a pull-down transistor that work together to transform the abrupt output signal into a smooth sigmoid-shaped signal, effectively mediating between the simple synapse array and the required smooth output characteristic.
Solution Approach 2:
The patent changes the electrical parameters of the output circuit by using transistors with specific characteristics (pull-up and pull-down transistors) to modify the output signal waveform. By controlling the switching behavior and conductivity of these transistors, the abrupt signal transitions are transformed into smooth sigmoidal transitions.
2Adaptability or versatility
If neuromorphic devices produce abrupt output signals, then circuit simplicity is maintained, but the ability to mimic brain-like functionality is reduced
Solution Approach 1:
The inverting circuit serves as an intermediary that adds the necessary signal conditioning capability to enable brain-like functionality. This intermediate stage transforms the raw synapse output into a biologically plausible sigmoid signal without requiring complete redesign of the entire neuromorphic system.
3Manufacturing precision
If the post-synaptic neuron includes inverting circuits with series-connected transistors, then output signal smoothness is improved, but transistor body connection complexity increases
Solution Approach 1:
The patent merges the body connections of the pull-up and pull-down transistors to a common node, simplifying the overall connection structure. This merging approach reduces the number of separate connection paths while maintaining the necessary electrical characteristics for generating smooth sigmoid output signals.
Data Source
AI summary
A neuromorphic device may include: a pre-synaptic neuron; a synapse electrically connected with the pre-synaptic neuron through a row line; and a post-synaptic neuron electrically connected with the synapse through a column line. The post-synaptic neuron may include a first inverter, the first inverter comprising a first pull-up transistor and a first pull-down transistor, a body of the first pull-up transistor and a body of the first pull-down transistor being electrically connected with a first output node of the first inverter.