Amplifier Compensation Circuit for High-Frequency PSRR Stability
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Solution Overview
Problem
Miller compensation in amplifiers leads to poor power supply rejection ratio (PSRR) at high frequencies due to power supply voltage variations appearing at the output, which is undesirable in electronic systems.
Innovation Solution
Incorporating a second compensation capacitor and a second isolating transistor with a biasing transistor in series, configured to maintain a stable node voltage despite power supply fluctuations, and using a voltage source circuit to bias transistors with a reference voltage invariant to power supply fluctuations, thereby reducing the impact of power supply ripples on the output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If Miller compensation is used to increase amplifier stability, then stability is improved, but power supply rejection ratio deteriorates at high frequencies
Solution Approach 1:
The compensation capacitor is divided into two segments: a first compensation capacitor connected between the output node and the gate of the first output transistor, and a second compensation capacitor connected between the output node and the gate of the second output transistor. This segmentation allows each capacitor to independently contribute to stability while minimizing their combined impact on PSRR, resolving the contradiction between stability improvement and PSRR degradation.
2Reliability
If additional current sources are used to improve PSRR, then power supply rejection ratio is improved, but offset, noise, and power consumption increase
Solution Approach 1:
The biasing transistor automatically adjusts the operating point of the isolating transistor based on the voltage at the compensation node, eliminating the need for external current sources or complex biasing circuits. This self-biasing mechanism maintains PSRR performance without introducing additional offset, noise, or power consumption penalties.
Data Source
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AI summary
A compensation capacitor can be added to an amplifier for stability. Disclosed are systems and methods for improving the power supply rejection ratio (PSRR) performance of an amplifier in the presence of one or more compensation capacitors.