Variable-Resistance Bias Circuit for Accurate Amplifier ON/OFF Control
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Solution Overview
Problem
Conventional bias circuits for amplifiers in TDD wireless communication systems face challenges in maintaining accurate on-off control due to fluctuations in gate current and voltage division, leading to inappropriate amplifier state switching.
Innovation Solution
A bias circuit design that includes a first and second power source connected in series to the amplifier's gate terminal, a changeover switch for switching between ON and OFF states, and a resistance value varying unit to adjust resistance values based on control signals, preventing voltage division and maintaining stable gate-source voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional bias circuit is used for amplifier on-off control in TDD systems, then the amplifier can be switched between ON and OFF states, but voltage division and gate current fluctuations cause inaccurate control and inappropriate state switching
Solution Approach 1:
The bias circuit dynamically adjusts the resistance value of the series connected resistor based on the amplifier's operating state. During ON state, the resistance is set to a first value optimized for saturation operation, while during OFF state, it is adjusted to a second value for proper cutoff. This dynamic adaptation eliminates voltage division issues and ensures accurate gate-source voltage control throughout switching transitions.
Solution Approach 2:
The invention changes the resistance parameter of the bias circuit resistor according to different operating conditions. By varying the resistance value between a first resistance value (for ON state) and a second resistance value (for OFF state), the circuit maintains optimal voltage distribution and prevents gate current fluctuations that would otherwise cause control inaccuracies.
2Device complexity
If a fixed resistance value is used in the bias circuit, then the circuit structure is simple, but voltage division occurs leading to unstable gate-source voltage during amplifier switching
Solution Approach 1:
Rather than using a complex multi-component circuit, the invention employs a single resistor whose resistance value dynamically changes based on the amplifier state. This approach maintains structural simplicity while achieving reliable switching control through parameter variation, avoiding the need for complex voltage division networks or multiple fixed resistors.
Solution Approach 2:
The bias circuit uses a resistor with variable resistance that adapts between a first resistance value during ON state and a second resistance value during OFF state. This parameter change approach ensures accurate gate-source voltage control without requiring complex circuit topologies, maintaining simplicity while improving switching reliability.
3Ease of operation
If the resistance value in the bias circuit is not adjusted, then the circuit operation is simple, but gate current increases cause voltage fluctuations leading to inappropriate amplifier state switching
Solution Approach 1:
The bias circuit automatically adjusts the resistor value in response to gate current changes during switching transitions. During ON state, the resistance is set to a first value that accommodates high gate current, while during OFF state, it switches to a second value that prevents voltage fluctuations. This dynamic adjustment maintains operational simplicity while ensuring voltage stability throughout the switching cycle.
Solution Approach 2:
The invention changes the resistance parameter of the bias circuit resistor based on the amplifier's switching state and gate current levels. By adjusting between a first resistance value (for high gate current during ON) and a second resistance value (for low gate current during OFF), the circuit maintains simplicity while preventing voltage fluctuations that would cause inappropriate state switching.
Data Source
AI summary
Included are: a first power source 3 configured to output a voltage required for a first gate bias voltage for turning a power amplifier 2 to an ON state; a second power source 4 configured to output a voltage required for a second gate bias voltage for turning the power amplifier 2 to an OFF state; a changeover switch 5 connected between the first power source 3 and the power amplifier 2 and configured to supply either the first gate bias voltage or the second gate bias voltage to the power amplifier 2 by switching a state between the first power source 3 and the power amplifier 2 to either an open state or a short-circuit state on the basis of a control signal related to on-off control of the power amplifier 2; and a resistance value varying unit 15 connected between the second power source 4 and the power amplifier 2 and configured such that a resistance value thereof is variable.