RF Amplifier Bias Circuit With Temperature-Compensated Gain Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional radio frequency amplifier circuits for mobile communication terminals require high precision power supplies and increased circuit complexity to manage bias currents for high and low power output operations, leading to inefficiencies and increased power gain variations across modes.
Innovation Solution
A radio frequency amplifier circuit with a bias circuit that generates adjustable bias currents using a control signal, incorporating temperature compensation transistors and a bias changing section to manage base currents, allowing for flexible configuration and reduced circuit scale, and utilizing multiple amplifiers with inversely proportional bias currents to stabilize power gain across modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radio frequency amplifier circuit is designed for enhanced linear characteristic in HSDPA system, then the linear characteristic is improved, but the current consumption is increased
Solution Approach 1:
The patent implements dynamic bias current control by switching between first and second bias currents based on operation mode. The bias circuit dynamically adjusts the bias current supplied to the amplifier transistor - using first bias current for high power output mode and second bias current for low power output mode, thereby adapting the linear characteristic to match the actual operation requirements and reducing unnecessary current consumption.
2Measurement precision
If high precision power supplies are used to control bias current, then the power gain control precision is improved, but the device complexity is increased
Solution Approach 1:
The patent changes the control parameter from voltage to current by directly controlling the bias current with a control signal. The bias circuit responds to the control signal by switching between predetermined first and second bias current values, thereby controlling the power gain without requiring high precision power supply voltage regulation, simplifying the power supply requirements while maintaining control precision.
3Adaptability or versatility
If multiple amplifiers are used to cover multiple communication systems, then the adaptability is improved, but the current consumption is increased
Solution Approach 1:
The patent implements a universal amplifier circuit that can operate in both high power output mode and low power output mode using the same amplifier transistor. By controlling the bias current to switch between first and second values, the single amplifier adapts to different communication systems (W-CDMA Release 99 and HSDPA), eliminating the need for separate amplifiers for different modes and reducing overall current consumption.
Data Source
AI summary
A bias circuit 12 includes: a transistor Q5 operable to supply, to an amplifier 11, a bias current in accordance with a base current supplied thereto; a transistor Q3 operable to pass a current in accordance with a reference voltage Vref; a transistor Q2 operable to correct, in accordance with the current passed by the transistor Q3, the base current to be supplied to the transistor Q5, so as to compensate a temperature characteristic represented by the transistor Q5; and a bias changing section (of a transistor Q4, and resistances R5, R6, and R7), connected to a base of the transistor Q5, operable to change, in accordance with a control voltage VSW, an amount of the base current to be supplied to the transistor Q5. The amplifier 11 amplifies, by using the bias current supplied by the bias circuit 12, a radio frequency signal having been inputted thereto.