CMOS Power Amplifier Bias Circuit for Impedance-Based Linearity
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Solution Overview
Problem
CMOS power amplifiers face challenges in commercialization due to low insulation voltages, large source grounding lead inductances, and deterioration in physical performance of conductive substrates, which hinder their ability to achieve linear characteristics comparable to HBT-based power amplifiers.
Innovation Solution
A power amplifier module with a bias circuit that supplies bias power by differently setting impedance between the input signal terminal and the reference power terminal and between the input signal terminal and ground, utilizing NMOS transistors in series and parallel configurations to control impedance and voltage levels, thereby improving linear characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If CMOS process technology is used for power amplifiers, then unit costs are reduced and multi-chip structure advantages are achieved, but insulation voltages are low and source grounding lead inductances are large
Solution Approach 1:
The patent introduces a bias circuit as an intermediary component between the power amplifier and ground/reference power terminals. This bias circuit actively compensates for the low insulation voltage and large inductance issues inherent in CMOS technology by providing controlled bias currents and voltages, thereby enabling CMOS power amplifiers to achieve performance comparable to HBT-based designs while maintaining cost advantages
2Ease of manufacture
If CMOS process technology is used for power amplifiers, then unit costs are reduced and multi-chip structure advantages are achieved, but source grounding lead inductances are large
Solution Approach 1:
The bias circuit serves as an intermediary that actively compensates for the harmful inductance effects. By introducing controlled bias currents through the bias circuit, the patent counteracts the voltage drops and signal distortions caused by large source grounding lead inductances, enabling CMOS power amplifiers to achieve linear characteristics comparable to HBT-based designs
3Reliability
If bias circuit is added to CMOS power amplifier, then linear characteristics are improved, but device complexity increases
Solution Approach 1:
The patent employs parameter changes by dynamically adjusting bias currents and voltages based on operating conditions. The bias circuit modifies key electrical parameters (bias current levels, voltage levels) to optimize linear characteristics across different power output levels, transforming a static design into an adaptive system that maintains high linearity without excessive complexity
4Reliability
If bias power is supplied by differently setting impedance, then linear characteristics are improved, but device complexity increases
Solution Approach 1:
The patent implements parameter changes by dynamically adjusting impedance values in the bias circuit based on operating conditions. Different impedance settings are applied to different signal paths (input signal terminal to reference power terminal, and input signal terminal to ground) to optimize linear characteristics. This transforms the bias circuit into an adaptive system that automatically adjusts its electrical parameters to maintain high linearity across varying power levels
Data Source
AI summary
There is provided a power amplifier module having a bias circuit, in which a bias power is supplied to an amplifier by differently setting an impedance between an input signal terminal and a reference power terminal and an impedance between the input signal terminal and a ground. The power amplifier module includes: an amplifier unit receiving a bias power to amplify an input signal; and a bias unit supplying the bias power to the amplifier, by differently setting an impedance between an input signal terminal transmitting the input signal therethrough and a reference power terminal transmitting a reference power having a predetermined voltage level and an impedance between the input signal terminal and a ground.