Circuit for a CAM

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This patent describes a novel circuit design for a Content Addressable Memory (CAM) that uses a CMOS inverter with a changeable resistor (Rfb) electrically connecting the inverter's input and output. The resistor can be dynamically adjusted, allowing the circuit to operate as both an analog CAM (aCAM) and a digital CAM (dCAM). This means the CAM can output not only binary responses but also analog values representing partial matches, enabling more flexible and gradient-based operations. The design also integrates memristors for non-volatile analog data storage, which can be used in neural networks and other advanced applications requiring associative or pattern-based data retrieval.

Use CasesContent extracted from patent full text and abstract with AI.

• High-speed search engines and database indexing where fast content matching is required.
• Machine learning hardware accelerators, including neural network training and inference units that benefit from associative memory.
• Pattern recognition in AI, such as image or signal processing where similarity matching is essential.
• Non-volatile memory devices that require both analog and digital data handling.
• Embedded systems for edge AI where power-efficient analog computing is advantageous.
• Flexible memory systems for reconfigurable computing and neuromorphic architectures.

BenefitsContent extracted from patent full text and abstract with AI.

• Enables CAMs to perform both digital and analog matching, supporting binary and continuous-valued associative search.
• Provides adjustable response characteristics—ranging from sharp digital to smooth analog transitions—via a tunable resistor, increasing application flexibility.
• Improved match measurement allows for degree-of-match output (not just exact/no match), which is valuable in fuzzy or approximate search tasks.
• Symmetrical and steep response curves enhance accuracy and density in high-performance associative memory.
• Integration with memristors allows for non-volatile analog data storage and efficient programming of matching thresholds.
• Simplified layout with identical circuit sections reduces manufacturing complexity and cost.
• Suitable for implementing advanced AI and neuromorphic systems that require hardware-level associative and gradient-based learning capabilities.

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Patent Abstract

The invention relates to a switching circuit with a CMOS inverter and a changeable resistor (Rfb), wherein the changeable resistor (Rfb) electrically connects the input (Vin) of the CMOS inverter to the output (Vout) of the CMOS inverter. The invention also relates to a CAM having such a switching circuit. As a result, a switching circuit can be produced which can operate like an analogue CAM and a digital CAM.