Power Amplifier Bias Circuit With Controllable Current Profile
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Solution Overview
Problem
Traditional power amplifier bias circuits struggle to maintain optimal bias conditions across a wide range of supply voltages, leading to degraded performance and increased leakage current, which shortens the standby time of portable communication devices.
Innovation Solution
A power amplifier bias circuit with a controllable current profile, utilizing a first transistor device as a switch and a plurality of resistors to determine the bias current through a current mirror, allowing for adjustable bias conditions and minimized leakage current across varying supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a regulated constant voltage is used as the bias signal source, then the bias condition is fixed, but the power amplifier performance is optimized only at nominal supply voltage and degraded at other supply voltages
Solution Approach 1:
The bias circuit transitions from a fixed regulated voltage source to a dynamic system that responds to supply voltage changes. The first transistor device acts as a switch that automatically adjusts the bias current based on the unregulated system voltage level, enabling the circuit to adapt to different supply voltage conditions while maintaining optimal performance.
Solution Approach 2:
The invention changes the parameter being controlled from fixed voltage to variable current. By using the unregulated system voltage directly and controlling current through transistor switching and resistor networks, the bias current automatically adjusts with supply voltage variations, maintaining optimal amplifier performance across different voltage conditions.
2Device complexity
If traditional current mirror bias circuits are used, then the circuit is simple, but leakage current flows when the power amplifier is switched off, shortening standby time
Solution Approach 1:
The invention extracts the switching function from the continuous current mirror bias circuit. By introducing a first transistor device that can completely switch off the bias current path, the circuit separates the bias generation function from the continuous current flow, allowing complete shutdown of bias current when the amplifier is not in use, thereby eliminating leakage current.
Solution Approach 2:
The bias circuit implements periodic action by switching the bias current on and off based on amplifier operation state. The first transistor device periodically connects or disconnects the bias current path, ensuring current flows only when needed (during amplifier operation) and completely stops during standby, eliminating continuous leakage.
Data Source
AI summary
A power amplifier bias circuit having a controllable current profile includes a first transistor device configured as a switch, and configured to receive a non-regulated system voltage, and a plurality of resistors configured to provide a current and configured to determine an amount of a bias current that flows through a second transistor device, where the second transistor device is part of a current mirror comprising a third transistor device and the amount of bias current flowing through the second transistor device determines a power output of the third transistor device.