Amplifier Bias Current Control with Replica and Inductor Sensing
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Solution Overview
Problem
Amplifiers in electronic devices face performance issues due to deviations in bias current caused by aging, temperature changes, and other factors, leading to undesirable shifts in output power.
Innovation Solution
A method and apparatus for monitoring and controlling bias current in amplifiers using techniques such as current mirrors, voltage measurements across inductors, gate-to-source voltage measurements, and feedback loops to dynamically adjust bias voltages and maintain target bias currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed bias voltage is applied to the amplifier, then the circuit design is simple, but the bias current deviates from the target value due to aging and temperature changes
Solution Approach 1:
The patent implements a feedback mechanism where the bias current is continuously monitored and compared to a target value. The control circuit adjusts the bias voltage dynamically based on the measured current, compensating for deviations caused by aging and temperature changes. This closed-loop feedback system maintains reliable bias current despite environmental variations.
Solution Approach 2:
The amplifier system performs self-diagnosis and self-adjustment by monitoring its own bias current and automatically correcting deviations. The control circuit uses the measured bias current to generate appropriate control signals that adjust the bias voltage, enabling the system to maintain optimal performance without external intervention.
2Ease of manufacture
If bias current is allowed to vary with aging and temperature, then the circuit operation is simple, but the output power shifts and performance degrades
Solution Approach 1:
The system continuously monitors the bias current and compares it to the target value, using the error signal to adjust the bias voltage. This feedback loop ensures that output power remains consistent despite aging and temperature variations, as the bias current is actively maintained at the desired level rather than allowing free variation.
Solution Approach 2:
The patent dynamically changes the bias voltage parameter in response to measured bias current deviations. By adjusting this electrical parameter based on real-time measurements, the system compensates for environmental effects and maintains consistent output power performance throughout the amplifier's operational life.
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
This approach ensures consistent amplifier performance, improves production yield, and mitigates reliability issues by compensating for bias shifts due to aging and other factors, allowing for the use of lower-cost IC technologies.
Implementation Method 1
a sensing circuit coupled to the inductor and the amplifier. The sensing circuit measures a voltage across the inductor and provides a measured voltage
Implementation Method 2
A bias circuit is coupled to the amplifier and generates a bias voltage to obtain a target bias current for the amplifier
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
Techniques for monitoring and controlling bias current of amplifiers are described. In an exemplary design, an apparatus may include an amplifier and a bias circuit. The amplifier may include at least one transistor coupled to an inductor. The bias circuit may generate at least one bias voltage for the at least one transistor in the amplifier to obtain a target bias current for the amplifier. The bias circuit may generate the at least one bias voltage based on a voltage across the inductor in the amplifier, or a current through a current mirror formed with one of the at least one transistor in the amplifier, or a gate-to-source voltage of one of the at least one transistor in the amplifier, or a voltage in a replica circuit replicating the amplifier, or a current applied to the amplifier with a switched mode power supply disabled.