Parallel Output Stage Amplifier Biasing for High Load Drive
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Solution Overview
Problem
Existing amplifier systems face challenges in enhancing load-driving capability without increasing quiescent power dissipation, bandwidth limitations, and cost-effectiveness, particularly when multiple amplifiers are combined in parallel configurations.
Innovation Solution
A system comprising a main amplifier and additional output stages, controlled by a class AB amplifier control circuit, allows for flexible and cost-effective load-driving enhancement by attaching additional output stages in parallel, with feedback mechanisms to manage quiescent power and thermal management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple amplifiers are placed in parallel to double current driving capability, then load-driving capability is improved, but quiescent power dissipation is doubled
Solution Approach 1:
The invention segments the amplifier system into a master amplifier and multiple slave amplifiers. The master amplifier handles control and signal processing, while slave amplifiers are dedicated solely to current driving. This segmentation allows the system to achieve high current driving capability without requiring multiple full-function amplifiers, thereby reducing quiescent power dissipation while maintaining enhanced load-driving capability.
Solution Approach 2:
The master amplifier serves multiple functions: it processes the input signal, generates control signals, and manages the operation of multiple slave amplifiers. This multi-functionality allows a single amplifier to control multiple current-driving stages, achieving high power output without proportionally increasing the number of active amplifying devices, thus reducing overall quiescent power consumption.
2Power
If multiple amplifiers are placed in parallel to double current driving capability, then load-driving capability is improved, but device complexity increases
Solution Approach 1:
The invention merges the control functions of multiple amplifiers into a single master amplifier. Instead of having each amplifier independently process signals and require separate feedback loops, the master amplifier consolidates all control functions and distributes commands to slave amplifiers. This merging reduces the number of independent control circuits, feedback paths, and isolation components needed, thereby simplifying the overall system architecture while maintaining enhanced current driving capability.
3Reliability
If resistors are used to isolate amplifiers at output nodes, then offset voltage differences are managed, but voltage drop and headroom are reduced
Solution Approach 1:
The invention introduces a current mirror circuit as an intermediary between the master amplifier and slave amplifiers. This current mirror acts as a mediator that transfers the control signal from the master to the slaves without requiring direct electrical connection at the output nodes. By using this intermediary, the system achieves proper signal distribution and offset voltage management without needing isolation resistors, thereby maintaining full voltage headroom and avoiding power loss in resistive elements.
Data Source
AI summary
Embodiments of an amplifier system with enhanced load-driving capability are disclosed. The amplifier system comprises a main amplifier and multiple parallel output stages. Each additional output stage receives a current signal proportional to the main amplifier output current and outputs the replica of the main amplifier output current. An amplifier control circuit in the main amplifier receives current signals representing the current of each additional output stage to set a quiescent current of the amplifier system accordingly to ensure stability while minimizing quiescent power dissipation. Advantages of the amplifier system embodiments include unlimited load driving capability in principle, greatly relieved burden on thermal management, cost-effectiveness, design flexibility over single chip solutions, controllable current biasing of each output stage attached to the system, and controllable quiescent power dissipation based on application.