Discrete-Gain Amplifier Cells for Low-Noise Variable Gain
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Solution Overview
Problem
Existing variable-gain amplifiers suffer from noise and nonlinearities introduced by analog variable-gain elements, which limit their dynamic range and introduce distortion, particularly in circuits with multiple overlapping gain stages.
Innovation Solution
The implementation of an incremental gain amplifier with discrete gain settings, utilizing multiple selectable signal paths and digital or analog gain control interfaces to incrementally select signal paths, thereby eliminating analog variable-gain elements and reducing noise and distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If analog variable-gain elements are used to provide continuous gain adjustment, then gain control flexibility is improved, but noise and nonlinearities increase
Solution Approach 1:
The amplifier is divided into multiple parallel signal paths, each with a fixed gain setting. Instead of using a single analog variable-gain element, the circuit segments the gain control function into discrete parallel paths that can be selectively activated. This segmentation eliminates the need for continuous analog adjustment while maintaining gain control flexibility through digital or analog selection signals.
Solution Approach 2:
Multiple parallel amplifier paths with different fixed gain settings are merged into a single output. The selection logic merges the output of the active signal path with the common output node, allowing the system to achieve variable gain functionality by combining multiple fixed-gain stages rather than relying on a single analog variable-gain element.
2Adaptability or versatility
If multiple overlapping gain stages are used to extend gain range, then gain adjustability is improved, but distortion increases
Solution Approach 1:
The gain adjustment function is segmented into multiple independent parallel paths, each with a specific gain setting. This eliminates the interaction and overlapping between gain stages that causes distortion, while still providing a wide gain range through the selection of appropriate paths.
Solution Approach 2:
Instead of cascading multiple gain stages to achieve variable gain (which causes distortion through overlapping), the invention inverts the approach by using parallel paths and selecting one at a time. This inversion of the traditional multi-stage architecture eliminates the harmful interactions while maintaining gain adjustability.
3Reliability
If discrete gain settings are used to reduce noise, then linearity is improved, but gain control resolution decreases
Solution Approach 1:
The gain control function is segmented into multiple discrete parallel paths with different gain settings. By providing many finely-spaced discrete gain options across the available range, the system achieves high resolution without requiring analog variable-gain elements, thus maintaining both linearity and fine gain control capability.
Solution Approach 2:
The gain parameter is changed in discrete steps across multiple parallel paths rather than continuously. By carefully designing the discrete gain values and providing sufficient number of steps, the system maintains high resolution gain control while avoiding the noise and nonlinearity associated with analog variable-gain elements.
Data Source
AI summary
An amplifier has an input section with one or more input cells and an output section with one or more output cells. Either the input section or the output section includes at least two cells that may be selected to provide discrete gain settings. A loop amplifier is configured in a feedback arrangement with the input section. The input and output sections may have multiple selectable cells to provide coarse and fine gain steps. The gain of the loop amplifier may be coordinated with the gain of the input section to provide constant bandwidth operation.