Power Amplifier Attenuator Bias Control for Gain Linearity
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Solution Overview
Problem
Existing power amplifier circuits face challenges in maintaining high accuracy linearity of gain as output power increases, leading to decreased gain and deteriorated linearity.
Innovation Solution
A power amplifier circuit design incorporating a first and second transistor, a bias circuit, and an attenuator with a diode-connected transistor and capacitor configuration, where the control voltage decreases with increasing power level, allowing continuous attenuation adjustment to maintain linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If an attenuator is switched in accordance with operation mode to reduce gain in low-power mode, then power consumption is reduced, but the linearity of gain deteriorates because gain decreases continuously as output power increases
Solution Approach 1:
The patent applies dynamics by continuously adjusting the attenuation amount based on the instantaneous output power level rather than using fixed operation-mode switching. The control circuit dynamically varies the attenuation in real-time to track the continuous change in gain characteristics, thereby maintaining linear gain control across the entire power range while preserving power-saving benefits.
Solution Approach 2:
The patent changes the attenuation parameter continuously according to the output power level. By varying the attenuation amount as a function of instantaneous power rather than maintaining fixed attenuation states, the system achieves continuous gain control that follows the natural gain compression curve, improving linearity while adapting to different power conditions.
2Power
If gain is maintained at high levels across all power ranges, then amplification performance is improved, but linearity deteriorates due to continuous gain decrease as output power increases
Solution Approach 1:
The patent employs feedback by continuously monitoring the output power level and using this information to adjust the attenuation amount. The control circuit receives feedback about the instantaneous power state and dynamically modifies the attenuation to compensate for gain compression, thereby maintaining both high gain performance and improved linearity across the full power range.
Solution Approach 2:
The patent applies preliminary anti-action by proactively introducing attenuation that counteracts the expected gain compression before it fully manifests. By anticipating the continuous gain decrease that occurs with increasing output power and applying compensatory attenuation adjustments, the system pre-corrects the gain non-linearity while maintaining overall high gain performance.
Data Source
AI summary
A power amplifier circuit includes a first transistor amplifying a first signal; a second transistor amplifying a second signal; a bias circuit supplying a bias current or voltage to a base or gate of the second transistor; and an attenuator attenuating the first or second signal in accordance with a control voltage supplied from the bias circuit. The attenuator includes a first diode to which the control voltage is supplied, a third transistor including a collector connected to a supply path of the first or second signal, an emitter connected to a ground, and a base to which the control voltage is supplied from the first diode, and a capacitor connected in parallel with the first diode. The control voltage decreases as a second signal power level increases. The third transistor allows part of the first or second signal to pass to the emitter in accordance with the control voltage.