LDO Regulator Feedback Compensation for Gain and Bandwidth
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Solution Overview
Problem
Conventional low dropout (LDO) voltage regulators face challenges in increasing voltage gain and bandwidth without increasing the size and current consumption of the transistor inside the amplifier, leading to reduced operational range and trade-offs between voltage gain and bandwidth.
Innovation Solution
The proposed LDO voltage regulator incorporates a negative resistor circuit connected between the reference voltage and the feedback resistor, which generates a compensation current to counteract loss current, thereby increasing voltage gain and bandwidth without increasing the size or current consumption of the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the size of the amplifier is increased to increase voltage gain, then the voltage gain is improved, but the operation range in saturation region is reduced and current consumption increases
Solution Approach 1:
The patent introduces a buffer as an intermediary component between the amplifier and the pass transistor. This buffer acts as a mediator that isolates the amplifier from the load variations, allowing the amplifier to operate in its optimal saturation region without being directly affected by changes in output current demands, thus maintaining both voltage gain and operation range
Solution Approach 2:
The patent changes the operating parameters of the amplifier by introducing the buffer, which modifies the load seen by the amplifier. This parameter change allows the amplifier to maintain its bias point and operation range while still achieving the desired voltage gain improvement
2Measurement precision
If the current is reduced to increase voltage gain, then the voltage gain is improved, but the bandwidth is reduced
Solution Approach 1:
The patent segments the circuit into distinct functional blocks: the amplifier stage and the buffer stage. This segmentation allows each stage to be optimized independently - the amplifier can be designed for high voltage gain with reduced current, while the buffer provides the current driving capability needed to maintain wide bandwidth without affecting the amplifier's gain performance
3Stability of the object's composition
If a buffer is added between the amplifier and pass transistor to shift low-frequency pole, then the stability is improved, but the device complexity increases
Solution Approach 1:
The buffer serves as an intermediary that simplifies the overall circuit design by providing a straightforward solution to the stability problem. Rather than attempting to compensate for poles through complex feedback networks or frequency compensation circuits, the buffer directly addresses the issue by isolating the amplifier from load effects, making the stability improvement more straightforward despite the added component
Data Source
AI summary
Disclosed herein is a low dropout (LDO) voltage regulator including an amplifier configured to receive a reference voltage through a negative input terminal, receive a feedback voltage through a positive input terminal, and amplify a difference between the feedback voltage and the reference voltage; a buffer which has an input connected to an output of the amplifier and an output and performs a buffering operation; a pass transistor configured to generate a driving current according to an output signal of the buffer; a voltage divider configured to form an output signal according to the driving current and generate a feedback voltage through a feedback resistor connected thereto; and a negative resistor circuit connected between the reference voltage and the feedback resistor and configured to generate a compensation current compensating for a loss current generated in the feedback resistor. In accordance with the present invention, the LDO voltage regulator, which greatly improves load regulation with a wide bandwidth by increasing a gain without increasing a size and current consumption of a transistor inside an amplifier, can be provided.