Amplifier Gain Control Using a Nonlinear DAC Response
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Solution Overview
Problem
Existing amplifier technologies face challenges in accurately controlling gain due to the non-linear response of amplifiers, which requires high-resolution digital-to-analogue converters (DACs), increasing complexity and size, and making it difficult to optimize gain control logic.
Innovation Solution
The use of a digital-to-analogue converter with a first non-linear response that is based on the non-linear response of the amplifier circuit, allowing for a lower resolution DAC to maintain precision by counteracting the non-linearity, resulting in a more efficient distribution of step sizes across the operational range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-resolution DAC is used to achieve accurate gain control, then gain control precision is improved, but device complexity and size increase
Solution Approach 1:
The patent changes the transfer characteristic parameter of the DAC from a conventional linear relationship to a non-linear relationship that is specifically designed to counteract the amplifier's non-linear response. This parameter change allows the system to achieve accurate gain control with a lower-resolution DAC, reducing device complexity and size while maintaining precision.
Solution Approach 2:
The patent applies preliminary anti-action by designing the DAC's non-linear transfer characteristic to pre-compensate for the amplifier's non-linear response. The DAC's output is intentionally non-linear in a way that counteracts the amplifier's non-linearity, so that the overall system response becomes linear and predictable, enabling precise gain control without requiring a high-resolution linear DAC.
2Adaptability or versatility
If a conventional linear DAC is used with a non-linear amplifier, then the relationship between digital input and gain is dictated by amplifier non-linearity, but flexibility in optimizing gain control is reduced
Solution Approach 1:
The patent applies inversion by reversing the conventional approach: instead of using a linear DAC and accepting the amplifier's non-linear response, the patent uses a non-linear DAC whose transfer characteristic is designed to invert or counteract the amplifier's non-linearity. This allows the system to achieve a linear overall response and provides flexibility in optimizing gain control for specific amplifier characteristics.
3Ease of manufacture
If the DAC has uniform step sizes, then the design is simpler, but the distribution of gain control resolution across the operational range is inefficient
Solution Approach 1:
The patent applies local quality by making the DAC's step sizes non-uniform across its operational range. The transfer characteristic is designed so that smaller step sizes are provided in regions where the amplifier is more sensitive to gain control changes, and larger step sizes are provided where the amplifier is less sensitive. This local adaptation of step size quality optimizes the distribution of gain control resolution across the operational range, improving overall efficiency.
Data Source
AI summary
An amplifier apparatus is arranged to amplify an input signal with a gain based on a digital gain control signal. The amplifier apparatus comprises a digital-to-analogue converter arranged to convert the digital gain control signal into an analogue gain control signal according to a first non-linear relationship between digital gain control signal and analogue gain control signal; and an amplifier circuit portion arranged to amplify the input signal with a gain based on the analogue gain control signal according to a second non-linear relationship between analogue gain control signal and gain. The first non-linear relationship is based on the second non-linear relationship.