Differential Feedback Calibration for PSRR and CMRR Balance
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Solution Overview
Problem
Existing amplifiers with differential negative feedback paths face challenges in optimizing Power-Supply Rejection Ratio (PSRR) and Common-Mode Rejection Ratio (CMRR), particularly in maintaining balanced gain in differential feedback paths to minimize power supply variations affecting output.
Innovation Solution
A differential feedback amplifier with an adjustable feedback network that calibrates the net gain of each feedback path to achieve equal gains, using passive and active elements, and common-mode bootstrapping to enhance PSRR and CMRR, especially in Class D amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a differential feedback amplifier uses fixed feedback paths, then the circuit structure is simple, but the Power-Supply Rejection Ratio (PSRR) and Common-Mode Rejection Ratio (CMRR) are degraded due to gain imbalance in the feedback paths
Solution Approach 1:
The feedback network is made adjustable through calibration to optimize PSRR and CMRR. The patent implements a calibration mechanism that allows the feedback path gains to be dynamically adjusted to achieve precise matching, transforming a static fixed-gain structure into a dynamically calibratable system. This resolves the contradiction by enabling high performance through calibration while maintaining a relatively simple base structure.
2Reliability
If the feedback network is made adjustable to improve PSRR and CMRR, then the rejection ratios are improved, but the device complexity increases
Solution Approach 1:
The patent changes the gain parameters of the feedback paths through calibration to achieve precise matching. By adjusting the net gain of each differential feedback path during calibration, the system optimizes PSRR and CMRR performance. This parameter adjustment approach allows performance improvement without fundamentally changing the circuit topology, thus managing the complexity trade-off.
3Reliability
If gain calibration is performed to balance differential feedback paths, then PSRR and CMRR are optimized, but the calibration process adds time and complexity
Solution Approach 1:
The calibration is performed in advance during manufacturing or initial setup to establish the optimal feedback path gains. By performing the gain balancing action beforehand, the system achieves optimized PSRR and CMRR without requiring continuous calibration during operation. This preliminary calibration approach resolves the time loss issue while maintaining high performance.
Data Source
AI summary
A differential feedback amplifier is provided with a feedback network wherein that feedback network is adjustable so as to improve the PSRR of the amplifier. In another aspect of the present invention, a differential feedback amplifier is provided with a feedback network wherein that feedback network is adjustable so as to improve the CMRR of the amplifier. In a further aspect of the present invention, a Class D amplifier is provided with a passive differential feedback, summing with an input current at a differential virtual ground produced by an amplifier which is a sub-section of the Class D amplifier.