Chopper-Stabilized Instrumentation Amplifier for Low-Frequency Accuracy
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Solution Overview
Problem
Instrumentation amplifiers face challenges in achieving accurate low-frequency measurements with low noise and low power consumption, particularly in medical devices where discrete time architectures introduce aliasing and chopper-stabilized designs suffer from bandwidth limitations and ripple issues.
Innovation Solution
A chopper-stabilized instrumentation amplifier with a differential architecture and a mixer amplifier that uses chopping at low impedance nodes and feedback to eliminate noise and offset, operating as a continuous time system to minimize aliasing and achieve stable measurements at low frequencies with very low power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a discrete time switched capacitor architecture is used, then the amplifier can achieve low power operation, but aliasing of noise and signals occurs undermining measurement accuracy
Solution Approach 1:
The patent replaces the discrete time switched capacitor architecture with a continuous time chopper-stabilized architecture. This substitution eliminates the sampling process that causes aliasing in discrete time systems, while maintaining low power operation through the chopper stabilization technique that removes offset and low frequency noise without requiring high bandwidth amplifiers.
2Measurement precision
If a chopper stabilized architecture is used, then noise and offset are removed from the output signal, but bandwidth is limited producing large ripple in the passband
Solution Approach 1:
The patent changes the operating parameters of the chopper-stabilized amplifier by using a higher chopper frequency and optimizing the bandwidth of the intermediate amplifiers. This allows the amplifier to achieve both good noise and offset rejection while minimizing passband ripple and maintaining sufficient bandwidth for the application.
3Use of energy by moving object
If chopper stabilization is implemented at low power, then power consumption is reduced, but dynamic limitations such as glitching occur
Solution Approach 1:
The patent implements feedback mechanisms that detect and correct glitching artifacts introduced by chopper stabilization. The feedback path monitors the output signal and compensates for dynamic limitations, allowing the amplifier to maintain signal stability while operating at low power levels.
4Measurement precision
If component matching and trimming are performed to achieve high accuracy, then measurement precision is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent employs chopper stabilization techniques that automatically compensate for offset and drift without requiring manual component matching or trimming. The chopper circuit periodically resets the amplifier state and removes accumulated errors, enabling high accuracy operation with standard off-the-shelf components and reducing both device complexity and manufacturing difficulty.
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 provides a stable, low-noise output for low-frequency signals, suitable for medical and general-purpose applications, by effectively eliminating noise and offset while maintaining low power consumption, thus enhancing measurement accuracy and device longevity.
Implementation Method 1
a chopper circuit up-modulates a measurement signal into a higher frequency band to remove noise and offset
Implementation Method 2
The instrumentation amplifier uses a differential architecture and a mixer amplifier to substantially eliminate noise and offset from an output signal produced by the amplifier. Dynamic limitations, i.e., glitching, that result from chopper stabilization at low power are substantially eliminated or reduced through a combination of chopping at low impedance nodes within the mixer amplifier and feedback.
Data Source
Figure 1
Figure 2~3d
Figure 4a~5
AI summary
This disclosure describes a chopper stabilized instrumentation amplifier (19) The amplifier is configured to achieve stable measurements at low frequency with very low power consumption. The instrumentation amplifier (10) uses a differential architecture and a mixer amplifier (14) to substantially eliminate noise and offset from an output signal produced by the amplifier. Dynamic limitations, i.e., glitching, that result from chopper stabilization at low power are substantially eliminated through a combination of chopping at low impedance nodes within the mixer amplifier (14) and feedback. (16) The signal path of the amplifier operates as a continuous time system, providing minimal aliasing of noise or external signals entering the signal pathway at the chop frequency or its harmonics. The amplifier can be used in a low power system, such as an implantable medical device, to provide a stable, low-noise output signal.