Low-Dropout Voltage Regulator With Feedback Gain for High PSRR
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Solution Overview
Problem
Designing a low dropout voltage regulator with high power supply rejection capability and improved efficiency is challenging due to smaller power supply voltage levels, which complicates achieving stable output voltages and noise rejection in applications like radio frequency circuits.
Innovation Solution
A voltage regulator apparatus comprising an operational amplifier, resistors, a driving transistor, and an amplifier circuit that forms a feedback loop to enhance gain and power supply rejection ratio, using a common gate and common source amplifier configuration to regulate output voltage and control transistors effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If power supply voltage level is reduced to achieve smaller voltage supply, then voltage level is lowered, but dropout voltage regulation becomes difficult and efficiency deteriorates
Solution Approach 1:
The voltage regulator is divided into multiple functional blocks: an operational amplifier for error amplification, a driving transistor for power control, and an amplifier circuit with specific gain for signal enhancement. This segmentation allows each block to be optimized independently, enabling effective voltage regulation even at low supply voltages where conventional single-stage designs fail.
Solution Approach 2:
The patent implements a feedback mechanism where the amplifier circuit senses the output voltage and feeds it back to the operational amplifier. This closed-loop feedback system continuously adjusts the driving transistor control signal to maintain stable output voltage, overcoming the regulation difficulties associated with low dropout voltages by dynamically compensating for voltage drops.
2Device complexity
If conventional regulator design is used with smaller voltage supply, then device complexity is reduced, but power supply rejection capability becomes insufficient
Solution Approach 1:
The patent enhances power supply rejection by adding a dimensional aspect to the circuit design: an amplifier circuit with specific gain inserted in the signal path between the operational amplifier and the output stage. This additional amplification stage operates in a different gain dimension, providing superior noise rejection without significantly increasing overall circuit complexity compared to conventional designs.
3Use of energy by moving object
If dropout voltage is reduced to achieve low dropout regulator, then voltage difference is minimized, but loop gain decreases and regulation stability worsens
Solution Approach 1:
The amplifier circuit with specific gain acts as an intermediary between the operational amplifier and the output stage. This intermediary block provides the additional loop gain needed to maintain regulation stability even when the dropout voltage is minimized. The amplifier circuit compensates for the reduced gain margin that results from operating with minimal voltage headroom.
Data Source
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AI summary
A voltage regulator apparatus includes operational amplifier, first resistor, second resistor, driving transistor, amplifier circuit, and output circuit. The operational amplifier has first input terminal coupled to reference voltage, second input terminal, and output terminal. The first resistor has first terminal coupled to second input terminal. The second resistor is coupled between first resistor and ground level. The driving transistor has control terminal coupled to output terminal of operational amplifier and first terminal coupled to second terminal of first resistor. The amplifier circuit is coupled to output terminal of operational amplifier and configured to sense output voltage of voltage regulator apparatus to amplify the sensed voltage with specific gain to regulate a transistor of output circuit. The transistor has control terminal controlled by amplifier circuit. The output voltage is generated at first terminal of the transistor.