Amplifier Supply Segmentation for High PSRR and Low THD
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional amplifiers suffer from inadequate power supply rejection ratio (PSRR), leading to significant total harmonic distortion (THD) due to large supply variations, especially in Class-G/H power amplifiers.
Innovation Solution
Incorporating a low dropout (LDO) voltage regulator to regulate the negative supply voltage, which is then used in both the first and second stages of the amplifier, effectively improving the power supply noise rejection by decoupling the gate of the input transistor from the negative supply voltage and enhancing the overall PSRR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional amplifier design is used, then device complexity is low, but power supply noise rejection is insufficient
Solution Approach 1:
An LDO voltage regulator is introduced as an intermediary component between the power supply and the amplifier stages. The regulator's output provides a clean, regulated voltage to the first and second amplifier stages, effectively blocking power supply noise from coupling into the signal path. This mediator approach achieves high PSRR (improving from -56 dB to -108 dB at 2 kHz) while adding only a single regulator component to the overall system.
2Use of energy by moving object
If Class-G/H power amplifier is used, then power efficiency is improved, but supply variation increases causing THD degradation
Solution Approach 1:
The power supply system is segmented into two independent paths: a regulated path providing clean voltage to the first and second amplifier stages, and an unregulated path providing current to the output stage. This segmentation allows the Class-G/H amplifier to maintain its power efficiency benefits while the regulated path ensures stable operating points for the signal processing stages, preventing THD degradation from supply variations.
Solution Approach 2:
Different quality levels of power supply are provided to different parts of the amplifier circuit. The first and second stages receive high-quality regulated voltage with excellent PSRR, while the output stage operates from the unregulated Class-G/H supply. This local quality differentiation allows each section to operate optimally - the signal stages require clean power for low distortion, while the output stage benefits from the efficiency of switched-mode operation.
Data Source
AI summary
An amplifier with high power supply rejection is disclosed. In an exemplary implementation, an amplifier includes a first stage configured to receive a signal to be amplified, a second stage comprising an input transistor coupled to the first stage, and further comprising at least one additional transistor, and a voltage regulator configured to received a first supply voltage and generate a regulated supply voltage, the first supply voltage coupled to the at least one additional transistor, the regulated supply voltage coupled to the first stage and the input transistor of the second stage to improve power supply noise rejection of the apparatus.