Doherty Power Amplifier Bias Control for Smooth Gain Transitions
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Solution Overview
Problem
The tracking mode applied to power amplifier circuits, including carrier and peak amplifiers, leads to deterioration of amplification characteristics, particularly due to abrupt changes in gain caused by dynamic adjustments in power supply voltage.
Innovation Solution
A power amplifier circuit design that includes a carrier amplifier, a peak amplifier, a combiner, bias circuits, and a modulation circuit or comparator circuit to control DC bias currents based on the power supply voltage, thereby stabilizing the amplification characteristics by adjusting the magnitude of DC bias currents and power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If tracking mode is applied to dynamically adjust power supply voltage to improve efficiency, then energy efficiency is improved, but amplification characteristics deteriorate due to abrupt gain changes
Solution Approach 1:
A current control circuit is introduced as an intermediary between the power supply voltage and the peak amplifier. This circuit converts abrupt voltage changes into smooth current transitions by integrating the voltage signal, thereby maintaining amplification characteristics while enabling dynamic power supply adjustment for efficiency improvement
Solution Approach 2:
The invention changes the parameter being controlled from voltage to current. By controlling the bias current of the peak amplifier through integration rather than directly adjusting voltage, the system achieves smooth transitions that preserve amplification characteristics while still enabling dynamic power management
2Device complexity
If discrete voltage levels are used in ET mode to simplify power supply control, then device complexity is reduced, but gain transitions become abrupt causing characteristic deterioration
Solution Approach 1:
The current control circuit acts as a mediator that smooths the transition between discrete voltage levels. By integrating the stepped voltage signal, it produces continuous current waveforms that prevent abrupt gain changes while maintaining the simplicity of discrete voltage level control
Solution Approach 2:
The system introduces dynamic current control based on the integrated voltage signal. The peak amplifier's bias current dynamically follows the envelope signal through the integration process, creating smooth transitions even when the power supply voltage changes in discrete steps
Data Source
AI summary
A power amplifier circuit includes a carrier amplifier, a peak amplifier, an external output terminal, a combiner that includes an input terminal connected to an output terminal of the power amplifier, an input terminal connected to an output terminal of the power amplifier, and an output terminal connected to the external output terminal, a bias circuit that supplies a DC bias current to the carrier amplifier, a bias circuit that supplies a DC bias current to the peak amplifier, and a current limit circuit that is connected between the power amplifier and the bias circuit and that is configured to change a magnitude of the DC bias current according to a magnitude of a power supply voltage applied to the power amplifier circuit.