Dual-Feedback LDO Circuit for Power Amplifier Switching Spectrum
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Solution Overview
Problem
Existing power amplifier control methods, whether current or voltage control, are hindered by the impact of control voltage slopes on switching spectrum performance, necessitating an improved low dropout regulator (LDO) power supply circuit and power amplifier design.
Innovation Solution
The LDO power supply circuit incorporates an operational amplifier, a PMOS transistor, and a resistance feedback network with two distinct feedback coefficients, connected between the transistor's drain and operational amplifier's input, enhancing the rising slope of the output voltage and thus improving switching spectrum performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional LDO power supply circuit with single feedback coefficient is used, then the circuit structure is simple, but the rising slope of output voltage is insufficient, degrading switching spectrum performance
Solution Approach 1:
The feedback network is segmented into multiple parallel branches, each with different feedback coefficients. The first feedback branch includes a first resistance and second resistance in series, while the second feedback branch includes a third resistance and fourth resistance in series. This segmentation allows different feedback paths to contribute differently to the overall feedback signal, enabling improved rising slope while maintaining manageable circuit complexity.
Solution Approach 2:
The feedback network dynamically adapts its effective feedback coefficient based on operating conditions. By configuring resistors with specific resistance relationships (R1+R2 < R3+R4), the circuit automatically utilizes different feedback paths depending on the output voltage level, achieving optimal rising slope during transient conditions while maintaining stability during steady-state operation.
2Speed
If the control voltage rising slope is increased to improve switching spectrum performance, then the power output and control effectiveness are enhanced, but the circuit requires more complex control mechanisms
Solution Approach 1:
The circuit employs a dual-branch feedback network that automatically adjusts the feedback signal based on output voltage conditions. The operational amplifier compares the feedback voltage with a reference voltage and adjusts the output accordingly. This feedback mechanism achieves rapid voltage rising slope without requiring complex external control circuits, as the adjustment is automatically performed by the feedback network configuration.
Solution Approach 2:
The feedback network utilizes resistance parameter relationships to control the rising slope. By designing the resistors such that (R1+R2) < (R3+R4), the circuit creates different effective feedback coefficients for different operating conditions. This parameter-based control achieves fast rising slope through passive component selection rather than active control circuitry.
Data Source
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AI summary
An LDO power supply circuit includes an operational amplifier, a first transistor, and a resistance feedback network. A negative electrode input end of the operational amplifier is configured to connect a control voltage . A positive electrode input end of the operational amplifier is an input end of the LDO power supply circuit. An output end of the operational amplifier is connected to a gate electrode of the first transistor. A source electrode of the first transistor is configured to connect a power supply voltage. A drain electrode of the first transistor is an output end of the LDO power supply circuit. The resistance feedback network is connected between the drain electrode of the first transistor and the positive electrode input end of the operational amplifier. The resistance feedback network comprises a first branch and a second branch, and the first branch and the second branch are connected in parallel. The first branch (101) forms a first feedback coefficient. The second branch forms a second feedback coefficient. The first feedback coefficient is different from the second feedback coefficient. The present disclosure further provides a power amplifier. Compared with the prior art, the present disclosure provides the power supply circuit and the power amplifier having a good switching spectrum performance.