Low-Noise Reference Signal Circuit With Switched Filtering
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Solution Overview
Problem
Existing circuitry for generating reference signals, such as in earbuds, faces challenges in reducing noise, which affects the quality of output audio, as current methods do not effectively minimize noise in reference signals.
Innovation Solution
A circuit comprising a filter unit with a transistor and an energy storage component, where the transistor is controlled to turn on and off by a control signal, configuring the filter unit as either an all pass or low pass filter to reduce noise within a specific frequency band, utilizing a high-impedance functional unit to minimize leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional reference signal generation circuits are used, then the circuit structure is simple, but the noise level in the reference signal is high
Solution Approach 1:
The circuit is divided into distinct functional blocks: a filter unit with transient response characteristics and a functional unit with high input impedance. This segmentation allows each block to optimize for its specific function - the filter unit for noise reduction and the functional unit for minimal loading effect - thereby achieving low noise output while maintaining reasonable circuit complexity
Solution Approach 2:
The filter unit acts as an intermediary component between the reference signal source and the functional unit. It temporarily stores energy and shapes the transient response to reduce noise within the frequency band of interest, mediating between the raw reference signal and the final low-noise output without requiring complex filtering circuits
2Object-affected harmful factors
If a filter circuit is added to reduce noise, then the noise level decreases, but the circuit complexity increases
Solution Approach 1:
The filter unit's parameters (time constant, cutoff frequency) are specifically designed to match the application's frequency band requirements. By adjusting these parameters, the circuit achieves effective noise filtering in the desired frequency range while maintaining a simple structure with minimal components
Solution Approach 2:
The filter unit serves multiple functions simultaneously: it filters noise, shapes the transient response, and provides impedance transformation. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby lowering overall circuit complexity while achieving effective noise reduction
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
This approach effectively generates low-noise reference signals by filtering out noise within the desired frequency band, improving the quality of audio output by reducing noise energy within that range.
Implementation Method 1
a filter unit (102) including a transistor (M) and an energy storage component (E)
Data Source
Figure 1
Figure 2A
Figure 2B~2D
AI summary
A circuit for low-noise reference signal generation comprising a filter unit and a functional unit. The filter unit comprises a transistor and an energy storage component. The transistor comprises a first node, a second node, a control node and a body node. The first node is configured to receive an input signal. The second node is configured to output a filtered signal. The control node is configured to receive a control signal for controlling the transistor to turn on or off. The body node is configured to couple to the input signal, the output signal or a signal which is similar to the input signal or the output signal. The energy storage component is coupled to the second node of the transistor. The functional unit is coupled to the second node of the transistor and the energy storage component. The functional unit has high input impedance.