Chopper-stabilized instrumentation amplifier and method for impedance measurement

Abstract

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 theamplifier 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.

Description

technical field

[0001] This invention relates to amplifiers, and more particularly to instrumentation amplifiers for precise signal measurements. Background technique

[0002] Instrumentation amplifiers are used to accurately measure a wide variety of test and measurement signals. For example, a medical instrumentation amplifier might be configured to measure physiological signals such as electrocardiogram (ECG), electromyography (EMG), electroencephalogram (EEG), pressure, impedance, and motion signals. Typically, instrumentation amplifiers are constructed as differential amplifiers with low offset, low drift, low noise, high common-mode rejection, high loop gain, and high input impedance. In many cases, instrumentation amplifiers may require careful matching and fine-tuning of circuit components to achieve high accuracy.

[0003] Instrumentation amplifiers may be constructed using discrete switched capacitor structures that obtain discrete signal samples. However, the ...

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