Apparatus and methods for amplifiers
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Solution Overview
Problem
Active devices, such as amplifiers, exhibit non-linearity leading to distortion in output signals, particularly intermodulation distortion, which is difficult to filter without degrading desired frequencies.
Innovation Solution
An integrated circuit with two single-ended gain stages in parallel, where one stage produces a high-quality amplified signal with minimal distortion and the other produces a poorly amplified signal with significant distortion, with the latter's output being inverted and added to the former to reduce intermodulation distortion in the final output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single amplifier stage is used to provide high gain amplification, then amplification of the input signal is improved, but intermodulation distortion increases
Solution Approach 1:
The amplifier is divided into two separate single-ended gain stages operating in parallel. Each stage contributes to the overall amplification while generating distortion products. By segmenting the amplification function, the patent enables subsequent cancellation of distortion products through signal combining, thus resolving the contradiction between achieving high gain and minimizing intermodulation distortion.
2Object-generated harmful factors
If filtering is applied to remove intermodulation distortion, then distortion is reduced, but desired frequencies are degraded
Solution Approach 1:
The patent converts the harmful distortion products generated by each amplifier stage into a beneficial element by using signal cancellation. The distortion products from two parallel stages are made equal in magnitude but opposite in phase, causing them to cancel each other out when combined. This transforms the harmful intermodulation distortion into a mechanism for distortion reduction, avoiding the need for filtering that would degrade desired frequencies.
Data Source
AI summary
Circuits and methods for reducing distortion in an amplified signal are disclosed. The circuits and methods may use multiple single-ended gain stages to produce multiple amplified signals. The amplified signals may be processed in combination to produce a resulting output signal having little, or no, distortion. The circuits may be implemented on a single chip as integrated circuits.