Sensor Amplifier Biasing and Noise Reduction
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Solution Overview
Problem
Existing resistive sensor systems face challenges with power consumption, noise, and production costs due to the need for multiple operational amplifiers and complex trimming processes for temperature compensation, while also lacking efficient amplification and linear continuous-time closed-loop operation.
Innovation Solution
A sensor arrangement utilizing a fully-differential amplifier with feedback paths and common mode control to provide bias and amplification, reducing power consumption and noise by reusing bias current for both sensor and amplifier, and implementing a ratiometric compensation system to stabilize the sensor bias point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple operational amplifiers and precision regulators are used for sensor bias and signal amplification, then measurement precision is improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent combines the sensor biasing function and signal amplification function into a single operational amplifier circuit. The non-inverting input of the op-amp serves as the bias voltage source for the Wheatstone bridge, while the same op-amp amplifies the differential output signal. This merging eliminates the need for separate bias regulators and multiple amplifiers, significantly reducing power consumption while maintaining measurement precision through the high input impedance and low noise characteristics of the op-amp.
Solution Approach 2:
The single operational amplifier performs multiple functions simultaneously: it provides the bias voltage for the sensor bridge, amplifies the small differential signal from the bridge, and provides temperature compensation through its feedback network. This multi-functionality reduces the total component count and power consumption while achieving the required measurement precision.
2Measurement precision
If multiple operational amplifiers are used for sensor bias and signal amplification, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the biasing circuitry and amplification circuitry into a single operational amplifier configuration. The op-amp's high input impedance naturally provides the bias voltage without requiring separate voltage regulators, and its feedback network simultaneously amplifies the sensor signal and provides temperature compensation. This reduces the device from requiring 4+ operational amplifiers to仅需 1, significantly simplifying the device while maintaining precision.
3Measurement precision
If complex trimming processes are implemented for temperature compensation, then measurement precision is improved, but manufacturing precision requirements increase and production costs increase
Solution Approach 1:
The operational amplifier's feedback network automatically compensates for temperature drift through its inherent negative feedback mechanism. The feedback resistors are configured to provide a temperature coefficient that counteracts the sensor's positive temperature coefficient, eliminating the need for manual trimming or complex calibration processes. The circuit self-adjusts to maintain measurement precision across temperature variations.
Solution Approach 2:
The patent employs negative feedback through the op-amp's feedback network to automatically compensate for temperature effects. The feedback path includes resistors with specific temperature coefficients that counterbalance the sensor's temperature drift, creating a self-correcting system that maintains measurement accuracy without requiring external trimming or calibration.
4Measurement precision
If multiple amplifiers are used for signal amplification, then measurement precision is improved, but sensor noise increases
Solution Approach 1:
By combining biasing and amplification into a single low-noise operational amplifier, the patent eliminates the noise contribution from multiple amplifier stages. The single op-amp configuration reduces the total noise figure while providing sufficient gain through its feedback network, avoiding the noise accumulation that would occur with cascaded amplifiers.
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
This approach achieves low-noise, low-power sensor bias and amplification with reduced production costs, enabling efficient temperature compensation and linear output, suitable for applications requiring high DC precision and low-frequency noise cancellation.
Implementation Method 1
a first output of the first operational amplifier is coupled to the first terminal of the sensor for amplifying signal variations from the sensor
Implementation Method 2
a feedback path from a second output of the first operational amplifier to a second terminal of the sensor, to provide a bias for the sensor
Data Source
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AI summary
A sensor arrangement comprising a differential amplifier (102) and a sensor (104) is provided. Thereby, a terminal of the sensor is coupled to an input (108) of the differential amplifier. An output (110) of the differential amplifier is coupled to the terminal of the sensor for providing a bias for the sensor.