LNA Bias Circuit for Stable Gain Under Low Supply Voltage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current low noise amplifier (LNA) circuits face challenges in maintaining a constant bias voltage as the power supply voltage changes, particularly when transitioning from 1.8V to 1.2V, which affects the amplifier's performance and gain characteristics.
Innovation Solution
A bias circuit is introduced that includes a current source capable of increasing the reference current with temperature, and a current-to-voltage conversion circuit that generates a constant bias voltage for a common gate transistor, ensuring stability across varying power supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the power supply voltage is lowered from 1.8V to 1.2V to reduce power consumption, then power consumption is reduced, but the bias voltage becomes unstable and gain characteristics deteriorate
Solution Approach 1:
The patent changes the parameter of reference current magnitude based on temperature conditions. The current source circuit adjusts the reference current to be larger at higher temperatures and smaller at lower temperatures, which compensates for temperature-induced variations in transistor characteristics and maintains stable bias voltage under different power supply conditions
Solution Approach 2:
The patent implements a feedback mechanism where the bias circuit monitors temperature and adjusts the reference current accordingly. The current source uses temperature-dependent resistance changes to automatically regulate the reference current, creating a closed-loop system that maintains bias voltage stability despite power supply voltage changes
2Device complexity
If a fixed bias voltage is applied to the common gate transistor, then the circuit is simple, but gain variations occur when power supply voltage changes
Solution Approach 1:
The patent transitions from a static bias voltage approach to a dynamic biasing scheme. The bias circuit actively adjusts the reference current based on temperature variations, making the bias voltage adaptive rather than fixed. This dynamic adjustment compensates for temperature effects on transistor parameters, maintaining gain stability without significantly increasing circuit complexity
Solution Approach 2:
The patent changes the electrical parameter of reference current dynamically based on temperature. By using temperature-dependent resistance in the current source, the system automatically modifies the bias conditions to compensate for thermal effects, achieving gain stability across varying power supply voltages and temperatures
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 proposed solution maintains a constant bias voltage and reduces gain variations in the LNA circuit, even when the power supply voltage changes, thereby enhancing the amplifier's performance and temperature compensation.
Implementation Method 1
a resistance value of the resistor decreases as temperature increases
Data Source
AI summary
A bias circuit and a low-noise amplifier circuit including the same provided. The bias circuit may be connected to a first transistor configured to amplify an input radio frequency (RF) signal and may be configured to provide a bias voltage to a second transistor that amplifies an output RF signal of the first transistor. The bias circuit may include a current source configured to receive a power supply voltage and generate a reference current, and a current-to-voltage conversion circuit configured to convert the reference current into the bias voltage and provide the bias voltage to a control terminal of the second transistor.