Differential Light Sensor Amplifier for Compact Optical Heart Rate Monitors
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Solution Overview
Problem
Existing optical heart rate monitor (OHRM) light sensor amplifier circuits have large footprints and high costs due to multiple components, and suffer from performance issues such as high power consumption and noise, as well as slow response times at high gains.
Innovation Solution
A compact optical heart rate monitor light sensor amplifier circuit design utilizing a differential amplifier with variable resistance circuits implemented using digital potentiometers and capacitors to set gain and reduce noise, coupled with a low-noise operational amplifier and a light sensor, allowing for efficient power management and improved response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple operational amplifiers and multiplexers are used in the amplifier circuit, then the circuit can achieve required amplification and signal processing functions, but the footprint and cost increase
Solution Approach 1:
The patent combines multiple operational amplifiers into a single operational amplifier by implementing a differential amplifier configuration that processes both differential signals and common-mode signals simultaneously. This merging reduces the component count from multiple op-amps to one, directly decreasing the circuit footprint while maintaining the required signal processing capabilities for optical heart rate monitoring.
Solution Approach 2:
The single operational amplifier in the patent is designed to perform multiple functions: differential amplification, common-mode rejection, and signal conditioning. By making the op-amp multi-functional, the circuit achieves the same performance as multi-op-amp designs without requiring additional components, thus reducing footprint and cost.
2Measurement precision
If high gain amplification is used to enhance signal strength, then the signal-to-noise ratio improves, but the response time becomes slower
Solution Approach 1:
The patent implements dynamic gain control through a variable gain amplifier stage that can adjust its amplification factor based on the input signal conditions. This dynamic adjustment allows the circuit to optimize between gain and bandwidth, achieving high signal-to-noise ratio when needed while maintaining fast response time by reducing gain when signal levels are adequate.
Solution Approach 2:
The patent changes the operating parameters of the amplifier circuit by using different capacitor values (C1, C2, C3) and resistor configurations to adjust the frequency response and gain-bandwidth product. By optimizing these parameters, the circuit achieves improved signal-to-noise ratio without excessively sacrificing response time, as the bandwidth is preserved through proper parameter selection.
3Reliability
If multiple components are used to achieve required amplification, then the circuit performance can be optimized, but the power consumption increases
Solution Approach 1:
The patent merges multiple amplification stages into a single operational amplifier with a differential input configuration. This consolidation reduces the total number of active components that consume power, while the differential architecture maintains high amplification performance by providing common-mode rejection and improved signal processing efficiency.
Solution Approach 2:
The circuit employs automatic gain control and adaptive biasing mechanisms that allow the amplifier to self-optimize its performance based on input signal conditions. This self-service capability ensures high amplification performance is maintained only when necessary, reducing overall power consumption by avoiding continuous high-gain operation.
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 solution reduces the component count and power consumption while enhancing noise reduction and response speed, effectively addressing the performance and cost issues of existing OHRM amplifier circuits.
Implementation Method 1
a light sensor to generate an electrical signal in response to light reflected by skin of a user
Implementation Method 2
a differential amplifier having an inverting terminal, a non-inverting terminal, and an output terminal
Implementation Method 3
a first variable resistance circuit coupled with a reference voltage, the inverting terminal of the differential amplifier, and an output terminal of the differential amplifier; a second variable resistance circuit coupled with the non-inverting terminal of the differential amplifier and the reference voltage
Data Source
AI summary
Embodiments include circuits, apparatuses, and systems for optical heart rate monitor light sensor amplifiers. In embodiments, an electronic circuit may include a differential amplifier having an inverting terminal, a non-inverting terminal, and an output terminal; a first variable resistance circuit coupled with a reference voltage, the inverting terminal of the differential amplifier, and the output terminal of the differential amplifier; a second variable resistance circuit coupled with the non-inverting terminal of the differential amplifier and the reference voltage; and a light sensor to generate an electrical signal in response to light reflected by skin of a user, the light sensor coupled with the non-inverting terminal and the inverting terminal of the differential amplifier. Other embodiments may be described and claimed.