Open-Loop RRAM Crossbar Read-Out Circuits for Fast Linear Sensing
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Solution Overview
Problem
Conventional crossbar circuits face limitations in speed, power consumption, and linearity due to operational amplifier-based read-out circuits, which are also susceptible to device mismatches and process, voltage, and temperature variations, and adjusting gain without impacting linearity is challenging.
Innovation Solution
The implementation of open-loop read-out circuits with two serially connected transistors and adjustable resistors, which convert bit line current to digital outputs without extra power consumption, offering faster settling times, improved energy efficiency, and maintaining linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If operational amplifier-based read-out circuits are used, then measurement precision is improved, but device complexity increases and power consumption increases
Solution Approach 1:
The patent extracts and eliminates the operational amplifier from the read-out circuit, replacing it with a simpler transistor-based open-loop circuit. This removes the complex feedback mechanism while maintaining sufficient measurement precision for crossbar circuit applications, directly addressing the contradiction between precision and complexity.
Solution Approach 2:
The patent uses simpler, less expensive transistor components instead of complex operational amplifiers. The open-loop transistor circuit achieves the required functionality with fewer, simpler components that are easier to manufacture and less power-intensive, resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If operational amplifier-based read-out circuits are used, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent removes the power-intensive operational amplifier and its feedback mechanism from the circuit. The simpler transistor-based open-loop circuit consumes significantly less power while maintaining adequate measurement precision for the crossbar array readout application.
Solution Approach 2:
The patent replaces the high-power operational amplifier with low-power transistor components. The open-loop configuration eliminates the continuous power consumption associated with op-amp feedback operation, achieving lower power consumption while preserving measurement accuracy.
3Measurement precision
If operational amplifier-based read-out circuits are used, then measurement precision is improved, but speed decreases
Solution Approach 1:
The patent extracts and removes the operational amplifier's feedback mechanism, which is responsible for slow settling behavior. The open-loop transistor circuit eliminates this feedback delay, enabling faster response and settling times while maintaining sufficient linearity for the application.
Solution Approach 2:
The patent replaces the slow operational amplifier with faster transistor components that have inherently faster switching and response times. The open-loop configuration removes the feedback-induced delays, achieving superior speed performance without sacrificing measurement precision.
4Adaptability or versatility
If gain is adjusted in conventional read-out circuits, then adaptability is improved, but linearity deteriorates
Solution Approach 1:
The patent implements dynamic gain adjustment capability in the open-loop transistor circuit through voltage-controlled resistance mechanisms. This allows the circuit to adapt to different signal levels and conditions while maintaining linearity, as the transistor's inherent characteristics allow for smooth, linear gain control without the feedback complications of op-amp circuits.
Data Source
AI summary
The present disclosure provides read-out circuits for crossbar circuits. A crossbar circuit may include a plurality of bit lines intersecting with a plurality of word lines and a plurality of cross-point devices. Each of the plurality of cross-point devices is connected to at least one of the plurality of word lines and at least one of the plurality of bit lines. The crossbar circuit may further include an output sensor that generates a digital output representative of a sum of currents flowing through one or more bit lines of the crossbar circuit. The output sensor includes a first transistor serially connected to a second transistor and an analog-to-digital converter configured to output the digital output. The read-out circuit is an open loop circuit. The read-out circuit may be selectively connected to one of the plurality of bit lines to perform a read operation.