Crossbar Transimpedance Amplifier Using Current Mirror Stabilization
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Solution Overview
Problem
Conventional transimpedance amplifiers (TIAs) in crossbar circuits are unstable due to complex capacitive loadings and current variations, which are exacerbated by interactions with operational amplifiers and varying current and voltage conditions during vector matrix multiplication (VMM) operations.
Innovation Solution
A transimpedance amplifier design incorporating an operational amplifier, a current mirror circuit, and resistors connected to a supply voltage, without feedback resistors in the operational amplifier loop, to stabilize output voltage against capacitive and current fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional transimpedance amplifiers are used in crossbar circuits, then the circuit can perform vector matrix multiplication operations, but the amplifier becomes unstable due to complex capacitive loadings and current variations
Solution Approach 1:
The patent removes the feedback resistor from the operational amplifier circuit, extracting the source of instability (capacitive loading effects in the feedback loop) while preserving the transimpedance amplification function through an alternative configuration using a current mirror and switched capacitor network
Solution Approach 2:
The patent changes the operational mode from a conventional voltage-feedback configuration to a current-mode operation with switched capacitors, fundamentally altering how the circuit handles signals and eliminating the stability issues associated with capacitive loadings in the feedback path
2Power
If feedback resistors are included in the operational amplifier loop, then the transimpedance amplifier can provide gain, but the output voltage becomes affected by capacitive loadings and current variations
Solution Approach 1:
The patent introduces a current mirror as an intermediary between the operational amplifier and the feedback network, isolating the op-amp from direct capacitive loading while maintaining signal transmission and amplification through the mirrored current path
Solution Approach 2:
The patent replaces the continuous analog feedback resistor with a switched capacitor network that operates in discrete time steps, substituting a static resistive feedback mechanism with a dynamic switching mechanism that achieves feedback without the associated stability problems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed TIA design generates an output voltage unaffected by capacitive loadings and current variations, enhancing circuit stability and improving the performance of analog-to-digital converters (ADCs) by increasing their dynamic range.
Implementation Method 1
a current mirror circuit connected to an output of the operational amplifier; wherein a first current flowing through the first transistor corresponds to the sum of the currents flowing through the first bit line, and wherein the first current is mirrored to a second current flowing through the second transistor
Implementation Method 2
The transimpedance amplifier generates an output voltage representative of a sum of currents flowing through a first bit line of the plurality of bit lines
Implementation Method 3
one or more resistors connected to the current mirror circuit and a supply voltage; wherein the output voltage generated by the transimpedance amplifier is represented as Vout=Vcc−I2*RFB
Data Source
AI summary
The present disclosure provides for transimpedance amplifiers 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 the cross-point devices is connected to at least one of the word lines and at least one of the bit lines. The crossbar circuit may further include a transimpedance amplifier to generate an output voltage representative of a sum of currents flowing through a first bit line of the plurality of bit line. The transimpedance amplifier may include an operational amplifier, a current mirror circuit connected to an output of the operational amplifier, and one or more resistors connected to the current mirror circuit and a supply voltage.