Doherty Amplifier Peak Bias Control for Fast Saturation Response
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Solution Overview
Problem
Doherty amplifier circuits experience a decrease in radio-frequency output signal quality due to the slow response time in detecting carrier amplifier saturation, leading to potential saturation and failure to maintain high communication quality.
Innovation Solution
A Doherty amplifier circuit with a control circuit that rapidly adjusts the operating state of peak amplifiers based on input control signals, preventing carrier amplifier saturation by activating peak amplifiers quickly in response to power fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a bias circuit detects saturation of the carrier amplifier to control the peak amplifier, then the Doherty amplifier circuit achieves high efficiency operation, but the response time becomes several tens of ns causing momentary saturation during power increases
Solution Approach 1:
The control circuit monitors the input signal power level and activates the peak amplifier before the carrier amplifier reaches saturation. By detecting power increases in advance and preemptively switching on the peak amplifier, the system prevents momentary saturation of the carrier amplifier, thereby maintaining both high efficiency and fast response without the several tens of ns delay associated with saturation detection methods
2Reliability
If the peak amplifier is activated quickly to prevent carrier amplifier saturation, then communication quality is maintained, but the circuit complexity increases
Solution Approach 1:
The control circuit implements a feedback mechanism that continuously monitors the input signal power level and dynamically adjusts the peak amplifier's operating state accordingly. When the monitored power level exceeds a predetermined threshold, the control circuit activates the peak amplifier; when power decreases below the threshold, it deactivates the peak amplifier. This closed-loop feedback system maintains high communication quality by preventing carrier amplifier saturation while using a relatively simple control architecture
Solution Approach 2:
The control circuit serves as an intermediary between the input signal and the peak amplifier, mediating the activation process. Rather than directly monitoring carrier amplifier saturation, the control circuit uses the input signal power level as an intermediate parameter to predict and control peak amplifier switching, simplifying the overall control logic while maintaining reliability
Data Source
AI summary
A Doherty amplifier circuit includes a carrier amplifier that amplifies a radio-frequency signal, a peak amplifier that amplifies a radio-frequency signal, and a bias circuit that supplies a bias current or a bias voltage to the peak amplifier. The peak amplifier includes one or more amplifier transistors that amplify a radio-frequency signal, and a state control circuit that controls the operating state of the one or more amplifier transistors on the basis of an input control signal.