Chopper-Stabilized Instrumentation Amplifier With Low-Aliasing Signal Path
Find Innovative SolutionsGenerate Solutions
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 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.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a discrete time switched capacitor architecture is used, then the amplifier can obtain discrete signal samples, but it produces undesirable aliasing of noise and signals that undermines 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 the ability to achieve low-offset and low-noise performance through chopper stabilization techniques.
Solution Approach 2:
The patent introduces a chopper circuit as an intermediary that modulates the measurement signal to a higher frequency band. This intermediary stage separates the low-frequency measurement signal from low-frequency noise and offset, allowing for accurate measurement without the aliasing problems of direct discrete-time sampling.
2Measurement precision
If a chopper stabilized architecture is used, then noise and offset are removed from the output signal, but the limited bandwidth produces large ripple in the passband
Solution Approach 1:
The patent employs dynamic elements including switched capacitors and feedback mechanisms that adapt the circuit behavior based on signal frequency. The chopper frequency is selected to be sufficiently high to push ripple to frequencies outside the passband, while the feedback loop dynamically compensates for bandwidth limitations to maintain stability and reduce passband ripple.
Solution Approach 2:
The patent optimizes the chopper frequency parameter to resolve the bandwidth-ripple tradeoff. By selecting an appropriate chopper frequency that is high enough to minimize passband ripple but not excessively high to waste bandwidth, the system achieves both good noise rejection and adequate 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 paths that monitor and correct for glitching and other dynamic limitations. The feedback mechanism detects deviations caused by chopper switching and applies corrective signals to maintain output stability, enabling low-power operation without sacrificing dynamic performance or reliability.
Solution Approach 2:
The patent incorporates compensation techniques that anticipate and preemptively counteract glitching effects. By designing the chopper circuit with built-in compensation elements that address switching transients before they propagate to the output, the system maintains stability during low-power chopper-stabilized operation.
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. The amplifier may be used for physiological signal sensing, impedance sensing, telemetry or other test and measurement applications.