Miller-Compensated Common-Mode Feedback for Stable High-Gain Amplifiers
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Solution Overview
Problem
Existing amplifying systems face stability issues when increasing gain, leading to restricted operations due to power changes, temperature changes, and shifts in common mode voltages, which are not effectively managed by conventional common-mode feedback circuits.
Innovation Solution
Incorporating a Miller compensation circuit within the common-mode feedback circuit to perform dominant pole compensation, using a Miller resistor and capacitor in series, which adds a negative zero to the pole-zero plot, thereby increasing stability without degrading system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If gain is increased in the amplifying circuit, then amplification capability is improved, but system stability deteriorates
Solution Approach 1:
The patent implements a common-mode feedback circuit that senses the common-mode voltage at the output and feeds it back to adjust the biasing of the amplifier stages. This feedback mechanism automatically regulates the operating point, allowing high gain operation while maintaining stability by correcting deviations in real-time
Solution Approach 2:
The patent changes the operating parameters by introducing a Miller compensation circuit that modifies the frequency response characteristics. By adding a compensation capacitor across a gain stage, the dominant pole is shifted to a lower frequency, ensuring phase margin and stability even with high overall gain
2Adaptability or versatility
If common-mode voltage shifts are not managed, then circuit operation becomes restricted, but adding conventional feedback circuits increases complexity
Solution Approach 1:
The patent merges the common-mode feedback function with the existing amplifier structure by utilizing the same output nodes for both differential signal extraction and common-mode sensing. The feedback path is integrated into the signal path without requiring completely separate sensing and control circuits, thus reducing overall complexity
Solution Approach 2:
The Miller compensation circuit serves dual purposes: it provides frequency compensation for stability while simultaneously acting as part of the common-mode feedback mechanism. This multi-functionality reduces the need for additional dedicated components, keeping the circuit compact despite enhanced capabilities
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
The solution allows for a significant increase in gain without reducing the overall system stability, ensuring stable operation of amplifiers like LNA, receiving amplifier, transmitting amplifier, and power amplifier by maintaining the swing level width for output voltages.
Implementation Method 1
The first Miller compensation circuit may include a first resistor and a first capacitor
Data Source
AI summary
An amplifying circuit may include: an amplifier configured to receive a first input voltage and output a first output voltage by amplifying the first input voltage; and a common-mode feedback circuit configured to enable the first output voltage to operate in a common mode by receiving the first output voltage and performing a feedback to adjust at least one feedback voltage applied to the amplifier based on the first output voltage. The common-mode feedback circuit may include a first Miller compensation circuit configured to perform dominant pole compensation by using a Miller effect for the common-mode feedback circuit. The first Miller compensation circuit may include a resistor and a capacitor.