Class-AB Amplifier De-Gain Stage for Capacitive Coupling Loss
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Solution Overview
Problem
Conventional class-AB amplifiers suffer from reduced efficiency due to capacitive coupling between driving signals, causing both PMOS and NMOS to be enabled simultaneously, especially at high frequencies, leading to inefficiencies similar to class-A operation.
Innovation Solution
Incorporation of a de-gain stage with a low-pass filter and control circuit to stabilize driving signals, limiting their swing during capacitive coupling events, thereby preventing simultaneous enablement of PMOS and NMOS.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional class-AB amplifier architecture is used, then the amplifier can operate at high frequency, but the capacitive coupling effect causes both PMOS and NMOS to be enabled simultaneously resulting in lower efficiency
Solution Approach 1:
The patent introduces a de-gain stage as an intermediary component between the amplifier stage and power stage. This de-gain stage generates a control signal based on the second driving signal to adjust the first driving signal, preventing simultaneous enablement of PMOS and NMOS while maintaining high-frequency operation capability
Solution Approach 2:
The de-gain stage implements a feedback mechanism where the control signal is generated according to the second driving signal and fed back to adjust the first driving signal. This feedback loop dynamically prevents the capacitive coupling effect from causing both transistors to be enabled simultaneously, thereby improving efficiency without sacrificing operating frequency
2Speed
If the amplifier operates at high frequency, then the speed performance is improved, but the capacitive coupling effect becomes more serious causing the amplifier to act like a class-A amplifier
Solution Approach 1:
The de-gain stage serves as an intermediary that simplifies the operation mode by actively managing the driving signals. It prevents the complex simultaneous conduction state from occurring, thereby maintaining the simpler class-AB operation mode even at high frequencies
3Device complexity
If no de-gain stage is used, then the device complexity is low, but the capacitive coupling causes leakage current and reduced efficiency
Solution Approach 1:
The de-gain stage is introduced as a minimal additional component that effectively prevents leakage current. By generating a control signal based on the second driving signal, it adjusts the first driving signal to prevent PMOS from being enabled when NMOS is conducting, thereby eliminating the leakage current issue with minimal added complexity
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
Enhances amplifier efficiency by stabilizing driving signals, preventing unnecessary current draw and improving overall performance.
Implementation Method 1
the de-gain stage comprises a low-pass filter and a control circuit, wherein the low-pass filter is configured to filter the second driving signal to generate a filtered second driving signal
Implementation Method 2
when the NMOS is enabled to draw current, the PMOS will also be enabled due to the unavoidable capacitive coupling effect between the driving signals
Data Source
AI summary
The present invention provides an amplifier including an input stage, an amplifier stage, a power stage and a de-gain stage. The input stage is configured to receive an input signal to generate an amplified signal. The amplifier stage is configured to generate a first driving signal and a second driving signal according to the amplified signal. The power stage comprises a first input terminal and a second input terminal, wherein the power stage is coupled to a supply voltage and a ground voltage, for receiving the first driving signal and the second driving signal from the first input terminal and the second input terminal, respectively, and generating an output signal.