3-Stage Miller Cross-Coupled Load based Photodiode Readout for Glucose Monitoring.

Area of Science:

• Biomedical Engineering
• Electronics Engineering
• Spectroscopy

Background:

• Non-invasive glucose monitoring is crucial for diabetes management.
• Existing methods often require invasive procedures or lack accuracy.
• Optical sensing techniques like Near Infrared Spectroscopy (NIRS) offer a promising alternative.

Purpose of the Study:

• To design and implement an innovative 3-stage, Miller-compensated, cross-coupled load photodiode front-end readout circuit.
• To utilize the Near Infrared Spectroscopy (NIRS) technique for non-invasive optical sensing of glucose.
• To achieve high gain and stability with low power consumption for a glucose monitoring system.

Main Methods:

• Design of a stable 3-stage open-loop amplifier with specific gain, phase margin, and GBW targets.
• Implementation of a transimpedance amplifier using a 0.18 μm CMOS technology node.
• Integration of the amplifier stages for a complete photodiode front-end readout.

Main Results:

• The 3-stage amplifier achieved a gain of 68.3 dB, a phase margin of 65°, and a Gain-Bandwidth Product (GBW) of 12.6 MHz, consuming only 0.26 mW.
• The transimpedance amplifier demonstrated a gain of 84.46 dB, a phase margin of 65°, and an input-referred noise of 20.4 pA/√Hz.
• The overall circuit achieved low power consumption (0.55 mW) from a 3.3 V supply.

Conclusions:

• The designed photodiode front-end readout is suitable for non-invasive glucose monitoring using NIRS.
• The circuit exhibits excellent performance characteristics, including high gain, stability, and low power consumption.
• This innovative design represents a significant advancement in optical biosensing for diabetes management.