Dynamic Bulk Biasing in Power Amplifiers for Better Compression
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Solution Overview
Problem
Power amplifiers in wireless communication systems face challenges in achieving high linearity and compression points due to nonlinear transfer functions, which result in intermodulation products and harmonic distortion, and existing linearization methods are not always effective.
Innovation Solution
A power amplifier design that drives the bulk node of a field-effect transistor with a dynamic bias voltage as a nonlinear function of the input signal's envelope, using a bias-voltage generation circuit that can be digital or analog, to improve the amplifier's linearity and compression point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional linearization methods (negative feedback, error feed forward, predistortion) are used to improve linearity, then linearity is improved, but device complexity increases
Solution Approach 1:
The patent changes the electrical parameter (bulk terminal voltage) of the transistor to achieve linearization. By dynamically adjusting the bulk terminal voltage based on the input signal envelope, the transistor's transfer function is modified to compensate for nonlinearities, improving linearity without adding complex feedback or predistortion circuits.
Solution Approach 2:
The bulk terminal acts as an intermediary element that mediates between the input signal and the output. By controlling the bulk terminal voltage, the patent indirectly influences the transistor's operation to achieve linearization, avoiding the need for direct feedback paths or complex compensation circuits.
2Reliability
If dynamic bias voltage is applied to bulk terminal to improve linearity, then linearity and compression point are improved, but manufacturing complexity increases due to SOI technology requirements
Solution Approach 1:
The patent utilizes the bulk terminal parameter, which is inherently available in SOI technology transistors. By exploiting this existing structural parameter and dynamically controlling its voltage, the patent achieves improved compression point while working within the constraints of SOI manufacturing processes.
3Ease of manufacture
If bulk terminal is biased with static voltage, then manufacturing is simplified, but linearity and compression point are limited
Solution Approach 1:
The patent transitions from static bulk terminal biasing to dynamic biasing. The bulk terminal voltage is now varied dynamically in response to the input signal envelope, enabling the transistor to maintain optimal operating conditions across different signal levels, thereby improving linearity and compression point while keeping the manufacturing approach relatively simple.
Data Source
AI summary
A power amplifier (20) for a transmitter circuit (10) is disclosed. The power amplifier (20) comprises at least one field-effect transistor (100, 100n, 100p) having a gate terminal (110, 110n, 110p) and a bulk terminal (120, 120n, 120p), wherein the at least one field-effect transistor (100, 100n, 100n) is configured to receive an input voltage at the gate terminal (110, 110p, 110n) and a dynamic bias voltage at the bulk terminal (120, 120n, 120p). Furthermore, the power amplifier (20) comprises a bias-voltage generation circuit (130). The input voltage is a linear function of an input signal. The bias-voltage generation circuit (130) is configured to generate the dynamic bias voltage as a nonlinear function of an envelope of the input signal.