Continuous-Time Chopper Instrumentation Amplifier for Low-Noise Sensing
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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 have limited bandwidth and ripple issues.
Innovation Solution
A chopper-stabilized instrumentation amplifier with a differential architecture and a mixer amplifier that modulates and demodulates signals at a clock frequency, using 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.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a discrete time switched capacitor architecture is used, then the instrumentation amplifier can be implemented, 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, thereby maintaining measurement accuracy while still enabling practical implementation of the instrumentation amplifier.
Solution Approach 2:
The patent changes the operational mode from discrete time sampling to continuous time operation with chopper stabilization. By modifying the time domain characteristics and using frequency modulation techniques, the system achieves both implementability and high measurement accuracy without aliasing errors.
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 employs feedback mechanisms within the chopper-stabilized architecture to extend the bandwidth and reduce passband ripple. By using the output signal to adjust the chopping process and compensate for limitations, the system maintains effective noise and offset elimination while expanding the operational bandwidth.
Solution Approach 2:
The patent introduces dynamic elements to the chopper-stabilized architecture, allowing the system to adapt its bandwidth characteristics. Through dynamic control of the chopping frequency and feedback paths, the amplifier achieves both low noise performance and extended bandwidth, reducing the static limitations of traditional chopper designs.
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 uses feedback mechanisms to detect and correct glitching caused by low-power chopper stabilization. By monitoring the output signal and adjusting the chopping process in real-time, the system maintains signal stability and reliability even while operating at reduced power consumption levels.
Solution Approach 2:
The patent implements compensatory measures in advance to prevent glitching before it occurs. By designing the chopper-stabilized architecture with built-in compensation circuits that anticipate and counteract potential instability, the system maintains reliable operation at low power without experiencing harmful dynamic limitations.
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 in low-power systems, such as implantable medical devices, by effectively eliminating noise and offset while maintaining minimal aliasing, thus enabling precise physiological signal measurement.
Implementation Method 1
a first modulator that modulates an amplitude of a differential input signal at a clock frequency to produce a modulated signal
Implementation Method 2
a mixer amplifier that amplifies the modulated signal to produce an amplified signal and demodulates the amplified signal at the clock frequency
Implementation Method 3
demodulates the amplified signal at the clock frequency
Implementation Method 4
a second modulator that modulates an amplitude of the output signal at the clock frequency
Implementation Method 5
a feedback path that applies the modulated output signal as a differential feedback signal to the modulated input signal
Implementation Method 6
a chopper circuit up-modulates a measurement signal into a higher frequency band to remove noise and offset
Data Source
AI summary
This disclosure describes a chopper stabilized instrumentation amplifier. The amplifier is configured to achieve stable measurements at low frequency with very low power consumption. 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 through a combination of chopping at low impedance nodes within the mixer amplifier and feedback. 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.