Current-Dumping Audio Amplifier With Clean Feedback Distortion Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional audio amplifiers face issues with nonlinearity of output power stages, poor thermal stability, and high voltage distortion in high frequency regions, which lead to increased harmonic and intermodulation distortion.
Innovation Solution
A high-fidelity audio amplifier design incorporating a feedforward error correction based on a balanced bridge principle, combined with a classical negative feedback loop, to minimize distortions and improve thermal stability, using a class B output stage without quiescent current and clean feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If negative feedback is used in audio amplifiers, then distortions are reduced and bandwidth is increased, but instability is generated and overall gain decreases
Solution Approach 1:
The patent divides the feedback system into two separate loops: a feedforward error correction loop that handles distortion cancellation without stability issues, and a negative feedback loop that provides gain control and bandwidth extension. This segmentation allows each loop to operate optimally without the drawbacks of a single combined loop.
Solution Approach 2:
The patent introduces an intermediary error detection and correction stage between the input and output stages. This intermediary loop detects distortion errors and provides correction signals without creating the stability problems associated with traditional negative feedback loops.
2Power
If conventional output power stages are used, then amplification is achieved, but nonlinearity increases and thermal stability deteriorates
Solution Approach 1:
The patent employs feedforward error correction that specifically targets and cancels nonlinearity distortions from the output power stage. By measuring the distortion introduced by the power stage and providing an equal and opposite correction signal, the system maintains high linearity while preserving the power stage's amplification capability.
3Manufacturing precision
If negative feedback loop is applied, then voltage distortion is reduced, but group delay increases in time domain
Solution Approach 1:
The feedforward error correction loop performs distortion cancellation in advance, before the signal passes through the negative feedback loop. This preliminary correction reduces the burden on the negative feedback loop, allowing it to operate with minimal group delay while still achieving low voltage distortion.
Data Source
AI summary
A high fidelity current dumping audio amplifier in which for achieving the best performance are combined the feedforward error correction and the negative feedback. The principle of feedforward error correction in a balanced bridge in A.C. is used, including the whole audio frequency amplifier, combined with a classical negative feedback that includes the items of the amplification chain likely to introduce distortions. The amplifier can be built in a current amplifier structure or in a voltage amplifier structure. The current amplifier structure contains an operational amplifier used as a voltage-current converter and signal de-phasing, two low power symmetrical current amplifiers operating in “A” class with a current mirror structure and a power stage in “B” class, with no quiescent current. The voltage structure of the amplifier contains an operational voltage amplifier, a low power amplifier operating in “A” class, and a power stage operating in “B” class.