Amplifier Offset Correction Using Auto-Zero Chopping Feedback
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Solution Overview
Problem
Amplifiers introduce errors such as voltage offset, 1/f noise, and drift, which are difficult to remove without using costly or slow-to-start low pass filters, especially in high-gain applications requiring stronger analog circuit precision.
Innovation Solution
The implementation of an auto-zero chopping demodulation scheme that couples the output of a first amplifier to track and hold circuits and summing nodes, allowing for the subtraction of errors without the need for a low pass filter, using a modulator to create differential components and a feedback loop to adjust the gain and correct for voltage offset, 1/f noise, and drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low pass filter is used to remove amplifier errors, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the error component from the amplified signal by using a second amplifier configured to amplify only the error signal. This separated error signal is then subtracted from the main signal, effectively removing the harmful amplifier errors without requiring a low pass filter.
Solution Approach 2:
The patent implements a feedback mechanism where the output of the second amplifier (error signal) is fed back and subtracted from the output of the first amplifier through a summing node. This feedback loop continuously corrects the amplifier errors by subtracting the extracted error component from the main signal.
2Measurement precision
If a low pass filter is used to remove amplifier errors, then measurement precision is improved, but startup time increases
Solution Approach 1:
The patent extracts the error component from the amplified signal by using a second amplifier configured to amplify only the error signal. This separated error signal is then subtracted from the main signal, effectively removing the harmful amplifier errors without requiring a low pass filter.
Solution Approach 2:
The patent implements a feedback mechanism where the output of the second amplifier (error signal) is fed back and subtracted from the output of the first amplifier through a summing node. This feedback loop continuously corrects the amplifier errors by subtracting the extracted error component from the main signal.
3Power
If amplifier gain is increased for high-gain applications, then signal strength is improved, but amplifier errors are amplified along with the signal
Solution Approach 1:
The patent segments the amplified signal into two separate components: the main signal containing the desired output from the first amplifier, and the error signal containing only the amplifier errors. This segmentation is achieved through the second amplifier that is configured to amplify only the error component, allowing independent processing of signal and error.
Solution Approach 2:
The patent extracts the error component from the amplified signal by using a second amplifier configured to amplify only the error signal. This separated error signal is then subtracted from the main signal, effectively removing the harmful amplifier errors without requiring a low pass filter.
Data Source
AI summary
An output of a first amplifier is coupled to an input of a first track and hold circuit and an input of a second track and hold circuit. An input of a first summing circuit is also coupled to an output of the first track and hold circuit and an output of the second track and hold circuit. In addition, an input of a second summing circuit is coupled to the output of the first track and hold circuit and the output of the second track and hold circuit. Moreover, an input of a third summing circuit coupled to an output of a modulator and an output of the second summing circuit, and an output of the third summing circuit coupled to an input of the first amplifier.