Linear Amplifier Output Correction for High-Current Linearity
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Solution Overview
Problem
Existing linear amplifiers suffer from non-ideal behavior in their high current output stages, leading to a voltage drop that compromises the linearity of the output signal, particularly in audio applications where distortion is undesirable.
Innovation Solution
Incorporating an output correction circuit with an operational transconductance amplifier or current mirror to feed back an error current that compensates for the voltage drop across the high current output stage, ensuring the output is linearly proportional to the input signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high current output stage is used to increase power output, then the power delivery capability is improved, but a voltage drop occurs across the output stage that compromises signal linearity
Solution Approach 1:
The patent implements a feedback mechanism where the output node is fed back to a summation node that combines it with the input signal. This feedback loop allows the system to detect the voltage drop across the output stage and compensate for it by adjusting the drive signal, thereby maintaining signal linearity while operating at high power levels.
Solution Approach 2:
The patent introduces an intermediary feedback path that mediates between the output stage and the input signal. This intermediary mechanism captures the output signal, processes it through the summation node, and uses it to correct the drive signal, effectively decoupling the power delivery function from the linearity requirement.
2Power
If the output stage is designed for high current operation, then power output is improved, but distortion increases due to non-ideal behavior
Solution Approach 1:
The feedback mechanism continuously monitors the output signal and compensates for distortion by combining the output feedback with the input signal at the summation node. This allows the system to maintain low distortion even when operating at high power levels by dynamically adjusting the drive signal based on actual output conditions.
Solution Approach 2:
The patent converts the harmful effect of the output stage voltage drop and non-ideal behavior into a beneficial correction mechanism. By feeding back the output signal and combining it with the input, the system uses the very signal that contains the distortion to generate the correction needed to eliminate that distortion.
Data Source
AI summary
A linear amplifier with correction circuit is provided. According to one aspect, a linear amplifier includes a high current output stage configured to produce an output voltage and current to deliver power to a load. An output correction circuit receives the output voltage from the high current output stage and produces an error current proportional to a voltage drop across the high current output stage. An input stage receives at least one input and produces a first input current. A current-to-voltage resistor receives produces a first voltage that depends on the first input current and the error current. A first unity gain voltage buffer receives the first voltage from the current-to-voltage resistor and outputs a second voltage that is input to the high current output stage. The first voltage is compensated by the error current to reduce the voltage drop across the high current output stage.