Amplifier Input Stage With Direct DAC-MOSFET Coupling for Low Distortion
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Solution Overview
Problem
High-fidelity amplifiers with current-output digital-to-analog converters face challenges in maintaining low distortion and high linearity due to high current consumption and overheating caused by multiple current sources, which impact the performance of the input stage.
Innovation Solution
The input stage design connects the source of the transistor directly to the signal terminal of the digital-analog converter, reducing the number of current sources and integrating the digital-analog and current-voltage converters on a single ASIC, with a cascode stage using a MOSFET transistor to maintain constant potential and minimize heating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple current sources are used in the current-to-voltage converter to cancel DC components and maintain constant potential, then signal quality and low distortion are improved, but current consumption and heating increase significantly
Solution Approach 1:
The invention extracts and removes the DC component cancellation function from the current-to-voltage converter circuit. By allowing the DC component to pass through to the virtual ground, the complex multi-current-source architecture is simplified to a single current source, eliminating the excessive current consumption and heating while preserving AC signal quality through the coupling capacitor.
Solution Approach 2:
The invention segments the signal processing into two distinct paths: AC signals are converted to voltage through the current-to-voltage converter with coupling capacitor, while DC components are directly routed to virtual ground. This segmentation allows each path to be optimized independently, reducing overall current consumption while maintaining signal integrity.
2Measurement precision
If multiple current sources are used to maintain constant potential at the digital-to-analog converter output, then distortion is reduced, but the device complexity and component count increase
Solution Approach 1:
The invention extracts the DC component handling function from the current-to-voltage converter and routes it directly to virtual ground. This removes the need for multiple current sources and their associated control circuitry, significantly reducing component count and device complexity while maintaining low distortion through proper AC signal path design.
Solution Approach 2:
The single current source in the invention serves multiple functions: it provides the necessary bias current for the transistor, handles AC signal conversion, and works in conjunction with the coupling capacitor to block DC while passing AC signals. This multi-functionality reduces the need for separate dedicated components for each function.
3Stability of the object's composition
If the transistor source is connected to a current source instead of directly to the digital-to-analog converter, then constant current operation is maintained, but heating and energy consumption increase
Solution Approach 1:
The invention introduces a coupling capacitor as an intermediary between the transistor source and the digital-to-analog converter output. This capacitor blocks DC components while allowing AC signals to pass, enabling the transistor to operate with stable bias conditions without requiring multiple high-current sources, thereby reducing heating while maintaining operational stability.
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 configuration reduces component count, compactness, and energy consumption, while preserving signal quality and minimizing overheating, thus enhancing the amplifier's performance and efficiency.
Implementation Method 1
a current-to-voltage converter with a voltage output, arranged between the signal terminal and the voltage output, the current-to-voltage converter having a transistor such that the gate of the transistor is connected to a voltage source
Implementation Method 2
the current source generating a direct current
Implementation Method 3
a digital-to-analog converter whose input forms the input for the digital signal to be converted
Implementation Method 4
a current-to-voltage conversion resistor arranged between the voltage output and a reference potential
Data Source
Figure 1~2
AI summary
The input stage (16) of a high-fidelity amplifier (10) with high linearity and a low distortion rate comprises: - an input (12) for the digital signal to be converted; - a voltage output (26) for the converted voltage; - a digital/analog converter (20), the input of which forms the input (12) for the digital signal to be converted, the digital/analog converter (20) having access to a signal terminal (24); - a voltage current conversion resistor (36) arranged between the voltage output (26) and a reference potential; and - a current/voltage converter (22) that has a voltage output and is arranged between the signal terminal (24) and the voltage outlet (26). The current/voltage converter (22) comprises a transistor (46). The source of the transistor (46) is only connected to the signal terminal (24) of the digital/analog converter (20).