Chopped Amplifier Ripple Filter Outside the Main Signal Path
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Solution Overview
Problem
Conventional chopped amplifiers with inline ripple filters suffer from reduced speed due to low pass filtering, and adding a feed-forward path increases input capacitance, reducing AC common-mode rejection and causing output glitches.
Innovation Solution
A chopped amplifier system with a ripple reduction filter placed outside the main signal path, using a digital controller and multiple filtering stages to distinguish and attenuate chopping ripple while handling large disturbances, maintaining fast transient response and wide common-mode range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If an inline ripple filter is used to reduce output ripple, then ripple reduction is achieved, but the speed of the chopped amplifier is significantly reduced
Solution Approach 1:
The ripple filter is extracted from the main signal path and placed in a separate feedback loop. This allows the main signal path to remain unobstructed for fast transient response, while the feedback loop handles ripple reduction without compromising speed.
Solution Approach 2:
A feedback loop acts as an intermediary mechanism to reduce ripple. Instead of placing the filter directly in the signal path, the feedback loop mediates between the amplifier output and the input, indirectly reducing ripple while preserving the main signal path's speed characteristics.
2Speed
If a feed-forward path is added to improve speed, then amplifier speed is improved, but input capacitance increases reducing AC common-mode rejection ratio
Solution Approach 1:
The feed-forward path is eliminated entirely. Instead, speed is maintained by removing the inline filter from the main signal path, achieving both fast transient response and preserved AC common-mode rejection without needing a feed-forward bypass.
3Speed
If a feed-forward path is added to improve speed, then amplifier speed is improved, but output glitches increase in response to common-mode transients
Solution Approach 1:
The feed-forward path is removed and the inline filter is extracted from the main signal path. This configuration achieves fast transient response through the unobstructed main path while avoiding the increased output glitches that result from feed-forward paths.
Data Source
AI summary
Embodiments relate to a chopped amplifier system where a ripple reduction filter placed outside of a main signal path is disclosed. The chopped amplifier system includes a chopped amplifier having an input terminal and an output terminal, where the input terminal receives an input signal and the output terminal provides an output signal including a ripple that is based on an offset voltage of the chopped amplifier. The ripple reduction filter is placed in a feedback loop path that receives a portion of the chopped amplifier's output signal and provides a feedback signal to the chopped amplifier that reduces the ripple at the output of the chopped amplifier. The ripple reduction filter includes a digital controller and other circuits that can handle large disturbances such as large signal slew rate events and large common-mode steps without reducing the effectiveness of the ripple reduction filter in reducing the ripple.