Chopper Amplifier Ripple Filtering for High-Accuracy ADC Drive
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Solution Overview
Problem
Chopper amplifiers used to drive analog-to-digital converters (ADCs) in data acquisition systems introduce increased ripple, compromising amplifier accuracy despite providing low offset and adequate bandwidth.
Innovation Solution
Implementing a balanced filter and chopper circuits with Miller capacitance multiplication and a parallel feedforward path, combined with AC feedback circuits, to reduce ripple and enhance bandwidth in chopper amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a chopper amplifier is used to achieve low offset and adequate bandwidth, then the amplifier can provide adequate bandwidth for the application, but the ripple increases due to switching which compromises amplifier accuracy
Solution Approach 1:
The amplifier is divided into multiple functional blocks: a first chopper amplifier stage for offset correction, a second chopper amplifier stage for additional conditioning, and an intermediate filter stage. This segmentation allows each stage to be optimized for its specific function while collectively achieving both low offset and reduced ripple.
Solution Approach 2:
An intermediate filter circuit is introduced between the first and second chopper amplifier stages. This intermediary filter removes the switching ripple generated by the first chopper stage before the signal enters the second stage, thereby preventing ripple propagation while maintaining the bandwidth benefits of the chopper architecture.
2Device complexity
If the ADC is driven directly from the data sensing terminal, then the system is simpler, but the ADC may interfere with the data acquisition and impact accuracy
Solution Approach 1:
A chopper amplifier circuit is introduced as an intermediary buffer between the data sensing terminal and the ADC. This buffer isolates the ADC from the sensing terminal, preventing the ADC from interfering with data acquisition while maintaining signal integrity and accuracy.
Solution Approach 2:
The chopper amplifier circuit provides self-service by automatically correcting its own offset errors through chopping techniques, eliminating the need for external offset calibration circuits and maintaining accuracy without adding significant complexity.
Data Source
AI summary
Described embodiments include an apparatus with a first amplifier having first inputs and first outputs. A second amplifier has second inputs and a second output. A first chopper circuit is coupled between third inputs and the first inputs. A second chopper circuit is coupled between the first outputs and the second inputs. A balanced filter is coupled to the second inputs.