Level-Shifted Amplifier Circuit for Low-Noise Large-Signal Operation
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Solution Overview
Problem
Conventional amplifier arrangements experience clipping during large signal operations and struggle to achieve good noise performance, particularly in microphone signal amplification from MEMS microphones.
Innovation Solution
An improved amplifier arrangement with a level-shifting structure that dynamically controls the potential at the second connection node between the current source and the input transistor, using a level-shifting element to adjust the voltage drop across the current source, ensuring a minimum voltage difference between the transistor's terminals and optimizing noise and distortion performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional amplifier arrangements are used for large signal operation, then signal amplification is achieved, but clipping occurs and noise performance deteriorates
Solution Approach 1:
The patent implements dynamic control of the second connection node potential through a level-shifting structure that adjusts the voltage drop across the current source based on input signal amplitude. For small signals, the structure maintains high voltage drop across the current source to optimize noise performance and PSRR. For large signals, it reduces the voltage drop to prevent clipping and improve signal-to-noise ratio, enabling adaptive operation across different signal conditions
Solution Approach 2:
The invention changes the operating parameters of the amplifier by dynamically adjusting the potential at the second connection node between the current source and input transistor. This parameter adjustment ensures the voltage difference between transistor terminals remains above a minimum level (e.g., saturation voltage plus 100 mV safety margin), preventing clipping while optimizing noise performance through controlled voltage drops across the current source
2Reliability
If the voltage drop across the current source is increased to improve noise performance, then power supply rejection ratio improves, but the voltage headroom for large signals is reduced
Solution Approach 1:
The level-shifting structure dynamically adjusts the voltage drop across the current source based on input signal conditions. For small input signals, it maintains a high voltage drop to optimize PSRR and noise performance. For large input signals, it reduces the voltage drop to provide sufficient voltage headroom, preventing clipping and extending the amplifier's dynamic range
Data Source
AI summary
An amplifier arrangement has an input transistor being connected between reference potential terminals by a current source and a current sink. An amplifier stage has an amplifier output coupled to a first connection node between the current sink and a first terminal of the input transistor by means of a feedback path, and an amplifier input connected to a second connection node between the current source and the second terminal of the input transistor. A level-shifting structure has a level-shifting element with one end connected to a reference connection, wherein the level-shifting element is adapted to perform a level-shifting of a potential at the second connection node with respect to a potential at the reference connection. The reference connection is coupled to one of the following: the amplifier output, the first connection node, a control terminal of the input transistor.