Amplifier Bias Linearization Circuit for Wider Envelope Bandwidth
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Solution Overview
Problem
Conventional adaptive/linearization biasing techniques for power amplifiers are sensitive to process, voltage, and temperature variations, have limited envelope bandwidth, and are not suitable for stacked transistors, rendering them sub-optimal for modern communication systems like 5G.
Innovation Solution
Separate bias and linearization circuits are coupled by a coupling circuit to provide modified bias signals, allowing independent optimization of linearization without stability limitations and enhancing envelope bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional adaptive biasing techniques are used, then bias control is achieved, but sensitivity to PVT variations increases and envelope bandwidth is limited
Solution Approach 1:
The patent divides the conventional single-loop adaptive biasing circuit into two separate circuits: a bias circuit and a linearization circuit. This segmentation allows each circuit to be independently optimized - the bias circuit for stability and PVT compensation, and the linearization circuit for envelope bandwidth and linearity improvement, thereby resolving the contradiction between reliability and adaptability.
Solution Approach 2:
The patent extracts the linearization function from the bias control loop by introducing a separate linearization circuit. This extraction removes the stability limitations that would constrain the envelope bandwidth, allowing the linearization circuit to operate independently with optimized bandwidth characteristics while the bias circuit maintains stable operation.
2Use of energy by moving object
If amplifiers operate in saturation, then efficiency is maximized, but linearity deteriorates due to nonlinear behavior
Solution Approach 1:
The patent employs feedback mechanisms in both the bias circuit and linearization circuit to continuously monitor and adjust operating conditions. The bias circuit uses feedback to compensate for PVT variations and maintain optimal bias points, while the linearization circuit uses feedback to cancel nonlinear distortions, enabling the amplifier to operate in saturation with improved linearity.
Solution Approach 2:
The patent dynamically changes bias parameters through the separate bias circuit to optimize the trade-off between efficiency and linearity. By adjusting bias voltages and currents based on operating conditions, the amplifier can maintain high efficiency in saturation while the linearization circuit compensates for nonlinear effects, effectively changing the operating parameters to satisfy both requirements.
3Device complexity
If a single loop is used for biasing and linearization, then circuit simplicity is maintained, but stability limitations reduce envelope bandwidth
Solution Approach 1:
The patent segments the single loop into two independent circuits - a bias circuit for DC bias control and a linearization circuit for AC signal linearization. This segmentation separates the stability-critical bias control from the bandwidth-critical linearization function, allowing each to be optimized independently without compromising overall system performance.
Solution Approach 2:
The patent introduces a coupling circuit as an intermediary between the bias circuit and linearization circuit. This coupling circuit enables coordinated operation of the two separate circuits while maintaining their independence, allowing the system to achieve both stability and wide envelope bandwidth without the limitations of a single constrained loop.
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AI summary
Bias arrangements for amplifiers are disclosed. An example bias arrangement for an amplifier includes a bias circuit, configured to produce a bias signal for the amplifier; a linearization circuit, configured to improve linearity of the amplifier by modifying the bias signal produced by the bias circuit to produce a modified bias signal to be provided to the amplifier; and a coupling circuit, configured to couple the bias circuit and the linearization circuit. Providing separate bias and linearization circuits coupled to one another by a coupling circuit allows separating a linearization operation from a biasing loop to overcome some drawbacks of prior art bias arrangements that utilize a single biasing loop.