Doherty Amplifier Bias Feedback for Sensitive Peaking Activation
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Solution Overview
Problem
Existing Doherty amplifier circuits face difficulties in activating the peaking amplifier with high sensitivity, leading to deterioration in the quality of radio-frequency output signals, particularly when the drive level of the carrier amplifier approaches saturation.
Innovation Solution
The proposed Doherty amplifier circuit incorporates a first and second bias circuit with negative feedback paths, differential amplifiers, and an inverting amplifier to stabilize bias currents and voltages, ensuring sensitive activation of the peaking amplifier by compensating for potential drops and maintaining high-quality radio-frequency output signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the peaking amplifier is activated based on saturation detection of the carrier amplifier, then the amplifier efficiency is improved, but the activation sensitivity is insufficient leading to deterioration in radio-frequency output signal quality
Solution Approach 1:
The patent implements feedback mechanisms where the bias circuit of the peaking amplifier receives feedback signals from the carrier amplifier's bias circuit. Specifically, when the carrier amplifier approaches saturation, its bias circuit generates a detection signal that is fed back to control the peaking amplifier's bias circuit, enabling sensitive and timely activation of the peaking amplifier to maintain output signal quality while preserving energy efficiency.
Solution Approach 2:
The patent introduces an intermediary bias control mechanism that mediates between the carrier amplifier and peaking amplifier. The bias circuit acts as an intermediary that translates the saturation state of the carrier amplifier into appropriate bias control signals for the peaking amplifier, enabling smooth and sensitive transition that maintains signal quality during the handover from carrier to peaking amplifier operation.
2Loss of energy
If the carrier amplifier operates with saturation to maintain high efficiency, then energy loss is reduced, but the drive level variation causes deterioration in output signal quality
Solution Approach 1:
The bias circuit of the carrier amplifier incorporates feedback mechanisms that continuously monitor the amplifier's operating state. When saturation is detected, the feedback signal triggers appropriate bias adjustments in the peaking amplifier, ensuring that the transition maintains precise output signal quality while preserving the energy efficiency benefits of saturation operation.
Data Source
AI summary
A first bias circuit, a second bias circuit, a first differential amplifier, a second differential amplifier, and an inverting amplifier are included. The first bias circuit has: a first bias output terminal from which first bias current or a voltage is output to a carrier amplifier; and a first monitoring terminal from which a first monitoring signal is output. The second bias circuit has: a second bias output terminal from which second bias current or a voltage is output to a peaking amplifier; and a second monitoring terminal from which a second monitoring signal is output. The first differential amplifier outputs the first bias control signal. The second differential amplifier outputs an amplified signal. The inverting amplifier outputs the second bias control signal resulting from inverting amplification of the amplified signal.