Cascode Common-Source TIA for Low-Noise Biosensor Readout
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Solution Overview
Problem
Conventional transimpedance amplifiers for biosensors face challenges in achieving low noise and low power consumption while maintaining high sensitivity and transimpedance gain, especially at low supply voltages, due to high input impedance and noise contributions from transconductance.
Innovation Solution
The development of a cascode common source transimpedance amplifier circuit implemented in both 180 nanometer CMOS and 32 nanometer carbon nanotube technology, which incorporates a cascode configuration with a source follower to minimize input impedance and noise, and a feedback resistor to enhance bandwidth and transimpedance gain, achieving low power consumption and high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional transimpedance amplifiers are used to achieve high transimpedance gain, then the gain is improved, but the input impedance increases and noise contribution from transconductance worsens
Solution Approach 1:
The amplifier is divided into two separate stages: a first transimpedance amplifier stage that converts input current to voltage, and a second voltage amplifier stage that provides additional gain. This segmentation allows each stage to be optimized independently, with the first stage having low input impedance and low noise, and the second stage providing high gain without adding significant noise to the overall system.
Solution Approach 2:
A voltage buffer or coupling stage acts as an intermediary between the current-to-voltage conversion stage and the final output stage. This intermediary stage isolates the low-impedance input stage from the high-gain amplification stage, preventing noise coupling and allowing optimal design of each stage's impedance characteristics.
2Volume of moving object
If amplifier size is reduced for miniaturization, then device size is improved, but sensitivity and signal detection capability worsen
Solution Approach 1:
The invention changes the operational parameters of the amplifier stages, specifically operating at low supply voltages (e.g., 1.8V or lower) and optimizing the transconductance values of the transistors. This allows achieving high transimpedance gain in a compact area by optimizing the electrical parameters rather than increasing physical size.
Solution Approach 2:
The amplifier uses a composite circuit architecture combining different amplifier topologies (transimpedance amplifier and voltage amplifier stages) with optimized transistor configurations. This composite approach allows achieving high performance in a compact footprint by leveraging the strengths of different circuit configurations rather than relying on a single large amplifier.
3Use of energy by moving object
If power consumption is reduced for low power applications, then energy efficiency is improved, but signal amplification capability and noise performance worsen
Solution Approach 1:
The amplifier stages are designed with dynamic biasing and adaptive gain control that allows the circuit to optimize its power consumption based on the input signal conditions. The transconductance values and bias currents are tuned to achieve the required signal-to-noise ratio while consuming minimal power, with the ability to adjust operating points dynamically.
Solution Approach 2:
The invention achieves low power consumption by changing the operational parameters to ultra-low voltage and current levels. The two-stage architecture allows the first stage to operate at very low power for current-to-voltage conversion while the second stage provides gain enhancement, with overall power consumption optimized by tuning the transconductance and bias conditions of each stage independently.
Data Source
AI summary
A biosensor for an analyte monitoring system. In one embodiment, the biosensor includes a cascode common source transimpedance amplifier circuit, an analog to digital converter, and an output circuit. The cascode common source transimpedance amplifier circuit is configured to receive an electrical current generated by an electrochemical reaction of an analyte on a test strip. The cascode common source transimpedance amplifier circuit is also configured to convert the electrical current to an analog voltage signal. The analog to digital converter is configured to convert the analog voltage signal to a digital voltage signal. The output circuit is configured to transmit a signal indicating a measured level of the analyte based on the digital voltage signal.