Ripple Reduction Loop Using Miller Capacitors for Chopper Amplifiers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing operational and instrumentation amplifiers face challenges in achieving effective ripple reduction and offset compensation, leading to residual ripple and noise, particularly in chopper-stabilized amplifiers.
Innovation Solution
The implementation of a Ripple Reduction Loop that utilizes Miller capacitors and a control amplifier to convert DC offset currents into square-wave currents, which are then rectified and integrated to correct the offset, eliminating the need for feed-forward paths and reducing ripple without introducing additional noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chopper stabilization is used to reduce offset, then offset compensation is improved, but ripple is introduced at the output
Solution Approach 1:
A feedback loop is implemented that detects the ripple generated by the chopper stabilization process and generates a compensating signal to cancel it. The loop includes a ripple detection mechanism that monitors the output and adjusts the chopper control accordingly, creating negative feedback to eliminate the harmful ripple while preserving the offset compensation benefit
Solution Approach 2:
An intermediary filtering stage is introduced between the chopper stabilization circuit and the amplifier output. This intermediary component processes the choppered signal to remove ripple frequencies before they appear at the final output, allowing the system to maintain offset compensation without transmitting the ripple to the output
2Measurement precision
If auto-zeroing is used to reduce offset, then offset compensation is improved, but noise is increased
Solution Approach 1:
The offset compensation function is extracted from the traditional auto-zeroing mechanism and implemented through a separate chopper stabilization loop. This extraction allows the system to achieve offset compensation through a different mechanism that does not inherently increase noise, as the chopper loop operates independently from the main signal path and can be filtered more effectively
Solution Approach 2:
The operating parameters of the offset compensation mechanism are changed by using chopper stabilization with specific frequency modulation instead of traditional auto-zeroing. By changing the frequency and duty cycle parameters of the chopper signal, the system achieves offset compensation while allowing for better noise filtering through frequency-selective approaches
3Object-generated harmful factors
If feed-forward paths are used for ripple reduction, then ripple is reduced, but device complexity is increased
Solution Approach 1:
The ripple reduction function is merged with the existing feedback loop structure rather than implementing a separate feed-forward path. The same feedback mechanism that provides gain control also handles ripple reduction, combining multiple functions into a single circuit pathway and reducing overall device complexity while maintaining effective ripple suppression
Data Source
AI summary
Ripple reduction loop for chopper amplifiers and chopper-stabilized amplifiers. The ripple reduction loop includes a first chopper, a first amplifier having an input coupled to an output of the first chopper, a second chopper having an input coupled to an output of the first amplifier, a second amplifier having an input coupled to an output of the second chopper, a third chopper, an output of the second amplifier having its output capacitively coupled to an input of the third chopper as the only input to the third chopper, a third amplifier coupled as an integrator having an input coupled to an output of the third chopper, an output of the integrator being coupled to combine with the output of the first amplifier as the input of the second chopper, and at least one Miller capacitor coupled between an output of the second amplifier and the input of the second amplifier. Various embodiments are disclosed.