Chopper Instrumentation Amplifier for Sensor Offset Removal
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Solution Overview
Problem
Existing instrumentation amplifiers face challenges in accurately removing offset voltages from sensors, leading to low system accuracy and common-mode rejection ratio due to complex ripple reduction loops that consume significant area and power.
Innovation Solution
A novel instrumentation amplifier design incorporating a high-pass filter and chopper modulation/demodulation circuit to eliminate offset voltages by converting DC offset signals into high-frequency signals, which are then filtered and compensated, reducing circuit complexity and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional ripple reduction loops are used to remove offset voltages, then offset voltage removal capability is improved, but circuit complexity and power consumption increase significantly
Solution Approach 1:
The patent changes the frequency parameter of the offset voltage signal by using a chopper circuit to modulate the DC offset voltage into an AC signal at a specific frequency. This frequency transformation enables the offset voltage to be separated from the original signal spectrum, allowing for effective filtering without requiring complex ripple reduction loops. The parameter change from DC to AC domain simplifies the overall circuit architecture while maintaining offset removal capability.
2Measurement precision
If traditional ripple reduction loops are used to remove offset voltages, then offset voltage removal capability is improved, but power consumption increases significantly
Solution Approach 1:
The patent extracts the offset voltage component from the signal by using a high-pass filter that specifically targets and removes the low-frequency or DC offset components while preserving the main signal. This extraction approach eliminates the need for power-intensive ripple reduction loops, as the offset removal is achieved through passive filtering elements that consume minimal power compared to active ripple reduction circuitry.
3Measurement precision
If chopper modulation is used to convert DC offset to high-frequency signal, then offset voltage removal is improved, but circuit complexity increases
Solution Approach 1:
The patent introduces a chopper circuit as an intermediary device that mediates between the DC offset voltage and the filtering stage. The chopper modulates the DC offset into an AC signal at a known frequency, which then becomes easier to filter using standard high-pass filter techniques. This intermediary transformation simplifies the overall filtering requirement compared to attempting to remove DC offset directly, thereby reducing the complexity of the complete system.
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 proposed design effectively removes offset voltages from both the amplifier and sensor, enhancing system accuracy and common-mode rejection ratio while minimizing circuit area and power consumption.
Implementation Method 1
chopper modulation/demodulation circuit to eliminate offset voltages by converting DC offset signals into high-frequency signals
Implementation Method 2
incorporating a high-pass filter and chopper modulation/demodulation circuit to eliminate offset voltages
Data Source
AI summary
An instrumentation amplifier can include: an input port configured to receive a sensor signal; a first-stage amplifier configured to amplify the sensor signal to obtain a first intermediate signal; a first high-pass filter circuit, having input terminals coupled to output terminals of the first-stage amplifier, and being configured to eliminate a signal that is in the first intermediate signal and associated with an offset voltage of the first-stage amplifier, in order to obtain a second intermediate signal; a first chopper, having input terminals coupled to output terminals of the first high-pass filter circuit, and being configured to perform chopper modulation and demodulation on the second intermediate signal to obtain a third intermediate signal; and a second-stage amplifier, having input terminals coupled to output terminals of the first chopper, and being configured to amplify the third intermediate signal to generate an output signal.