Chopper-Stabilized Current-Sense Amplifier for Low-Noise Precision
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Solution Overview
Problem
Existing current-sense amplifiers face limitations in high-precision measurements due to output signal offsets and low-frequency noise, which are not adequately addressed by existing technologies.
Innovation Solution
The proposed solution involves a current-sense amplifier arrangement that chops the signal derived from a current-voltage converter using a chopper circuit, followed by amplification with a fully differential amplifier and common mode feedback, and subsequent digital dechopping to reduce noise and offset, utilizing separate voltage domains for chopper stabilization and analog-to-digital conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional current-sense amplifier is used to measure current or voltage signals, then the measurement can be performed, but the output signal contains offset and low-frequency noise that limits measurement precision
Solution Approach 1:
The patent applies chopping (periodic switching) to modulate the input signal to a higher frequency, amplifying the chopped signal, and then dechopping it in the digital domain. This periodic action moves the signal spectrum away from low-frequency noise and offset, thereby improving measurement precision while eliminating the harmful low-frequency interference
Solution Approach 2:
The patent introduces a chopper circuit as an intermediary that modulates the input signal before amplification. This intermediary transforms the signal into a frequency domain where amplification can occur without being affected by low-frequency noise and offset, which are then removed during digital dechopping
2Adaptability or versatility
If high supply voltages or currents are processed, then the measurement range is extended, but the complexity of the circuit increases and standard CMOS technology cannot be used
Solution Approach 1:
The patent segments the circuit into two separate voltage domains: a first voltage domain for the chopper and part of the amplifier that processes high-voltage signals, and a second voltage domain using standard CMOS for the ADC and digital dechopper. This segmentation allows each domain to be optimized independently, reducing overall circuit complexity while maintaining voltage domain adaptability
Solution Approach 2:
The patent transitions from a single voltage domain to a multi-voltage domain architecture, adding the dimension of voltage domain separation. This allows the system to handle high supply voltages while using standard CMOS technology for digital processing, effectively resolving the conflict between voltage adaptability and device complexity
Data Source
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AI summary
A current-sense amplifier arrangement comprises a resistor (8) coupled to a first voltage source (9) and a feedback differential amplifier (20), that amplifier comprising a first amplifier stage and a second amplifier stage. The first amplifier stage is supplied by the first voltage source (9) and adapted to receive a chopped differential voltage (10) derived by a current flowing through the resistor. The second amplifier stage is supplied by a second voltage source and adapted to receive a differential signal provided by the first stage and adapted to provide an output signal having a common mode voltage. A dechopper (51) is supplied by a voltage derived by the second voltage source, the dechopper coupled to an output of the second stage of the feedback differential amplifier.