Dual-Compensation Bias Circuit for Stable Amplifier Base Bias
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Solution Overview
Problem
Power amplifiers in wireless communication systems face linearity deterioration due to temperature-induced changes in base bias levels, which complicates the design with additional circuit requirements for accurate temperature sensing.
Innovation Solution
A dual compensation bias circuit that generates and compensates base bias currents using dual temperature compensation functions, reflecting ambient temperature changes through a current generating circuit and temperature compensation transistors with current mirror structures, ensuring stable base bias levels across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a PTAT bias is used to increase external bias current at high temperature, then linearity performance is improved, but circuit complexity increases due to additional external circuits required
Solution Approach 1:
The patent merges the temperature sensing function and bias current generation function into a single integrated circuit block. The temperature sensing circuit is combined with the bias circuit to directly generate compensation currents without requiring separate external temperature sensing components, thereby improving linearity while reducing circuit complexity.
Solution Approach 2:
The bias circuit is designed to perform multiple functions: it senses temperature changes, generates compensation currents, and provides bias currents to the power amplifier all within a single circuit structure. This multi-functional design eliminates the need for separate external circuits while maintaining improved linearity performance across temperature variations.
2Measurement precision
If additional external circuits are added for temperature sensing, then temperature sensing accuracy is improved, but the circuit becomes more complicated
Solution Approach 1:
The circuit performs self-temperature sensing using internal components rather than requiring external temperature sensors. The temperature sensing function is self-contained within the bias circuit, allowing accurate temperature detection while maintaining a simple overall circuit structure.
Solution Approach 2:
The temperature sensing circuit is nested within the bias circuit structure, with the sensing elements integrated into the existing circuit topology. This nested arrangement allows accurate temperature sensing to be achieved without adding separate external circuit blocks, thereby avoiding increased complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively maintains linearity and reduces performance deviations in power amplifiers by stabilizing base bias currents, improving output power gain and reducing AM-AM distortion and ACLR performance across temperature changes.
Implementation Method 1
when the amplifying device is operated at a high temperature, a turn-on voltage Vth of the PN junction between the base and the emitter (base-emitter) is lowered due to the temperature characteristics of a device of the HBT
Implementation Method 2
a temperature compensation transistor connected between a second end of the second resistor and the ground, and connected to an amplifying transistor of the amplifying circuit while having a current mirror structure
Data Source
AI summary
A bias circuit includes a current generating circuit generating a first compensation current and a second compensation current, in which an ambient temperature change is reflected, based on a reference current, a first temperature compensation circuit generating a first base bias current, based on the first compensation current, to output the first base bias current to a base node of an amplifying circuit, and a second temperature compensation circuit generating a second base bias current, based on the second compensation current, to output the second base bias current to the base node of the amplifying circuit.