Low-Voltage Bias Tracking in Power Amplifier Circuits
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Solution Overview
Problem
Existing power amplifier devices consume high power and incur significant costs due to the high voltage applied to bias circuits, especially when using high-electron mobility transistors (HEMTs) or laterally-diffused metal-oxide semiconductor (LDMOS) transistors for high-power applications, necessitating a reduction in power consumption and costs.
Innovation Solution
A power amplifier device design that includes a first transistor for power amplification and a second transistor for monitoring, both supplied with distinct power supply voltages, where the bias circuit is powered by a lower voltage supply and adjusts the bias voltage based on the drain or source current of the second transistor, allowing for reduced power consumption and cost-effective implementation using low-withstand-voltage elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high voltage is applied to the bias circuit to enable high-power operation of HEMT or LDMOS transistors, then power amplification capability is improved, but power consumption of the bias circuit increases and costs increase
Solution Approach 1:
The power supply system is segmented into two distinct voltage sources: a first power supply terminal providing high voltage (e.g., 40V) for the power amplification transistor, and a second power supply terminal providing low voltage (e.g., 5V) for the bias circuit. This segmentation allows each subsystem to operate at its optimal voltage level, enabling high power amplification capability while keeping bias circuit power consumption low.
Solution Approach 2:
Different parts of the circuit are assigned different voltage qualities: the power amplification transistor receives high voltage to achieve high power output, while the bias circuit receives low voltage to minimize power consumption. The bias circuit locally generates the required bias voltage for the power transistor without needing to withstand high voltage itself, creating local quality differentiation in voltage levels across the circuit.
2Power
If high voltage is applied to the bias circuit for high-power operation, then power amplification capability is improved, but manufacturing costs increase due to requirement of high-withstand-voltage elements
Solution Approach 1:
The circuit is segmented such that only the power amplification transistor needs to withstand high voltage, while the bias circuit operates at low voltage. This segmentation allows the bias circuit to use standard low-cost components rather than expensive high-withstand-voltage elements, significantly reducing manufacturing costs while maintaining high power amplification capability.
Solution Approach 2:
The bias circuit uses low-withstand-voltage elements that are cheaper and more readily available than high-withstand-voltage components. By designing the bias circuit to operate at low voltage from the second power supply terminal, the patent employs cost-effective components for the bias generation function while the high voltage is isolated to only the power amplification transistor.
3Power
If the bias circuit is designed to operate at high voltage for high-power applications, then power output is improved, but device complexity increases due to requirement of high-withstand-voltage elements
Solution Approach 1:
The power supply system is divided into two independent channels: a high voltage channel for the power amplification transistor and a low voltage channel for the bias circuit. This segmentation simplifies the bias circuit design by eliminating the need for high-withstand-voltage components, capacitors, and other protective elements, thereby reducing overall device complexity while maintaining high power output capability.
Solution Approach 2:
The operating voltage parameter of the bias circuit is changed from high voltage to low voltage. By generating the bias voltage at low level from the second power supply terminal and using it to control the power transistor, the patent changes the voltage parameter where it matters (bias generation) while maintaining high voltage where needed (power amplification), thus reducing complexity.
Data Source
AI summary
A power amplifier device includes: a first power supply terminal for inputting a first power supply voltage; a first transistor for power amplification that (i) includes a first gate to which a bias voltage is applied, and (ii) is supplied with power from the first power supply terminal; a second power supply terminal for inputting a second power supply voltage lower than the first power supply voltage; a second transistor for monitoring that (i) includes a second gate to which the bias voltage is applied, (ii) is supplied with power from the first power supply terminal or the second power supply terminal, and (iii) imitates an operation of the first transistor; and a bias circuit that is supplied with power from the second power supply terminal and generates and adjusts the bias voltage according to a drain current or a source current of the second transistor.