Voltage Regulator Amplifier Feedback Loop Power Supply Rejection
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Solution Overview
Problem
Conventional voltage regulators suffer from low power supply rejection ratio due to direct influence of supply voltage on the output voltage, leading to inefficiencies in voltage regulation.
Innovation Solution
Incorporating an amplifier between the control node and the control terminal of the second transistor, which separates the direct current bias points, and utilizing a feedback loop with a reference voltage independent of the supply voltage to maintain stability and reduce the influence of supply voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the control node is directly connected to the control terminal of the first transistor, then the voltage regulator structure is simple, but the power supply rejection ratio is low due to direct influence of supply voltage on output voltage
Solution Approach 1:
An amplifier is introduced as an intermediary component between the control node and the control terminal of the first transistor. This amplifier decouples the direct connection, allowing the control node to track the supply voltage through the amplifier's output rather than directly, thereby improving power supply rejection ratio while maintaining structural simplicity
Solution Approach 2:
The voltage regulator is divided into distinct functional segments: a first current path with the first transistor, a second current path with the second transistor, and an amplifier segment. This segmentation allows independent optimization of each segment's function, with the amplifier specifically handling the control signal processing to reject supply voltage variations
2Ease of manufacture
If the control node directly tracks the supply voltage, then the bias point is simple to establish, but the influence of supply voltage variations on the voltage between control terminal and input terminal increases
Solution Approach 1:
The amplifier provides feedback control by continuously monitoring the control node voltage and adjusting its output to the control terminal accordingly. This feedback mechanism maintains the desired bias point while compensating for supply voltage variations, reducing their harmful influence on the voltage between control terminal and input terminal
Solution Approach 2:
The amplifier changes the parameter relationship between the control node and control terminal by providing voltage amplification and isolation. Instead of a direct 1:1 voltage relationship, the amplifier transforms the control node voltage to an appropriate level for the control terminal, changing the electrical parameter characteristics to reduce supply voltage influence
Data Source
AI summary
A voltage regulator (10) comprises a first transistor (13) which couples an input terminal (11) of the voltage regulator (10) to an output terminal (12) of the voltage regulator (10) and a second transistor (16). The first and the second transistors (13, 16) form a current mirror structure. Further on, the voltage regulator (10) comprises a control node (17) which is coupled to the input terminal (11) of the voltage regulator (10) via the second transistor (16) and which is coupled to the output terminal (12) of the voltage regulator (10) via a feedback circuit (28). Furthermore, the voltage regulator (10) comprises an amplifier (22) with an input terminal (23) which is coupled to the control node (17) and an output terminal (24) which is coupled to a control terminal (21) of the second transistor (16).