Multi-Stage Power Amplifier Feedback for Low-Distortion Audio
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Solution Overview
Problem
Existing power amplifiers require high-precision circuit elements to improve distortion characteristics, leading to high costs.
Innovation Solution
A power amplifier configuration with multiple amplifiers and feedback circuits that apply negative feedback to reduce distortion without the need for high-precision components, extending the frequency range of negative feedback beyond the audible band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high-precision circuit elements are used to improve distortion characteristics, then distortion characteristics are improved, but cost increases
Solution Approach 1:
The patent applies negative feedback by connecting the output terminal back to the input terminal through a feedback circuit containing resistors and capacitors. This feedback mechanism automatically corrects distortion in the amplified signal without requiring high-precision circuit elements, thereby improving distortion characteristics while maintaining low cost
Solution Approach 2:
The patent changes the feedback circuit parameters (resistor values, capacitor values) to optimize distortion correction. By adjusting these parameters, the feedback circuit effectively reduces distortion across the audible frequency range without needing expensive high-precision components
2Manufacturing precision
If negative feedback is extended to higher frequencies beyond the audible band, then distortion in the audible range is reduced, but circuit complexity increases
Solution Approach 1:
The feedback circuit is designed to extend negative feedback into ultrasonic frequencies beyond the audible band. This extended feedback range allows the circuit to correct distortion more effectively across all audible frequencies while using a relatively simple RC feedback network rather than complex active correction circuits
Solution Approach 2:
The feedback circuit serves multiple functions: it corrects distortion in the audible range, extends feedback to ultrasonic frequencies, and does so using a simple passive RC network. This multi-functionality reduces overall circuit complexity compared to using separate circuits for each function
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Improves distortion characteristics at a lower cost by applying more negative feedback in higher frequencies, reducing distortion in the audible range without requiring expensive high-precision circuit elements.
Implementation Method 1
a feedback circuit configured to negatively feed back a mixed signal of the mixing node to an input of the first amplifier
Data Source
AI summary
A power amplifier includes a first amplifier configured to amplify an input signal and output, from a first output, a first signal in which the input signal is amplified, a second amplifier configured to amplify the first signal and output, from a second output, a second signal in which the first signal is amplified, a third amplifier configured to amplify the second signal and output, from a third output, a third signal in which the second signal is amplified, a capacitor connected between the first output and a mixing node, a first resistor connected between the second output and the mixing node, a first inductor connected between the third output and the mixing node, a second inductor connected between the mixing node and a load, and a feedback circuit configured to negatively feed back a mixed signal of the mixing node to an input of the first amplifier.