Difference Amplifier Feedback Circuit for Common-Mode Rejection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Previous amplifiers that reject high common mode voltages often attenuate both common mode and differential signals, leading to degraded signal quality due to noise amplification.
Innovation Solution
A difference amplifier circuit comprising first and second amplifiers, buffer amplifiers, and feedback voltage dividers that allow for high common mode rejection without differential signal attenuation, utilizing input impedances and current sense impedances to isolate differential signals from common mode voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If common mode voltage rejection is implemented using previous techniques, then common mode voltage rejection is improved, but differential signal quality deteriorates due to attenuation and noise amplification
Solution Approach 1:
The circuit is divided into separate differential and common mode processing paths. The differential input signal is processed through one path while the common mode voltage is processed through a separate path, allowing independent optimization of each function without interfering with the other.
Solution Approach 2:
A dedicated common mode amplifier acts as an intermediary to sense and process the common mode voltage separately. This intermediary component allows the common mode rejection function to be implemented without directly affecting the differential signal path, thus maintaining signal quality.
2Object-affected harmful factors
If common mode voltage is attenuated using previous techniques, then common mode rejection is improved, but differential signal is attenuated requiring amplification that increases noise
Solution Approach 1:
The attenuation function is segmented and applied only to the common mode signal path through the common mode amplifier, while the differential signal path remains unaffected. This selective attenuation avoids the need to amplify the differential signal, thereby preventing noise amplification.
Solution Approach 2:
The common mode voltage component is extracted from the combined signal using the common mode amplifier, allowing it to be attenuated independently. This extraction enables common mode rejection without requiring amplification of the remaining differential signal, thus avoiding noise introduction.
3Power
If differential signal is amplified to compensate for attenuation, then output signal level is improved, but signal quality deteriorates due to amplified noise
Solution Approach 1:
The common mode component is extracted and handled separately, allowing the differential signal to maintain its original level without requiring compensatory amplification. This extraction approach preserves signal quality while still achieving the desired output level through the differential path.
Solution Approach 2:
The common mode amplifier serves as an intermediary that handles the common mode voltage separately, allowing the differential signal path to operate without attenuation. This mediator enables the differential signal to reach the desired output level without requiring amplification that would introduce noise.
Data Source
AI summary
Apparatus and methods for a difference amplifier are provided. In certain examples, the difference amplifier can provide high common mode rejection without differential signal attenuation. In an example, a difference amplifier circuit can include first and second amplifiers, first and second buffer amplifiers, a first feedback voltage divider coupled between an output of the first buffer amplifier and an output of the second amplifier, and a second feedback voltage divider coupled between an output of the second buffer amplifier and an output of the first amplifier.