Low-Noise Voltage Regulator With Capacitive Feedback Loop
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Solution Overview
Problem
Conventional low noise voltage regulators introduce noise that limits the performance of electronic circuits and systems, particularly in noise-sensitive applications like phase locked loops and data converters, due to noise generated by error amplifiers and resistor networks, which also increase area and bandwidth limitations.
Innovation Solution
A low noise electronic voltage regulator design featuring a regulating transistor, an error amplifier with a feedback loop, and a second amplifier configured as a replica with unity gain to provide a reference voltage, along with a transconductance amplifier and a filter to reduce noise, utilizing transconductance gains and a reference current source to generate a regulated DC output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feedback resistors are used in the voltage regulator, then the output voltage can be regulated, but noise is generated by the resistors and error amplifier
Solution Approach 1:
The patent removes the feedback resistors from the circuit entirely. Instead of using resistors to provide feedback voltage, the invention uses a capacitor connected between the output node and inverting input node, eliminating the noise source associated with resistors while maintaining voltage regulation functionality.
Solution Approach 2:
The patent introduces an intermediary capacitor as the feedback element. This capacitor mediates the feedback function without generating thermal noise like resistors would. The capacitor works in conjunction with the error amplifier to provide the necessary feedback signal for voltage regulation.
2Reliability
If additional amplifiers and resistor networks are added to increase feedback gain, then reference voltage can be amplified, but area increases and noise is added
Solution Approach 1:
The error amplifier performs multiple functions: it compares the feedback voltage with the reference voltage, amplifies the error signal, and drives the regulating transistor. The existing error amplifier is utilized to its full potential rather than adding separate amplification stages, thereby avoiding additional area consumption.
Solution Approach 2:
The patent changes the feedback network configuration from resistive dividers to a capacitive feedback path. This parameter change in the feedback mechanism allows for high feedback gain without requiring additional amplifying stages or resistor networks, thus avoiding area expansion.
3Reliability
If multi-stage error amplifiers are used, then voltage regulation is achieved, but significant noise is added to the output
Solution Approach 1:
The patent segments the feedback function from the amplification function. The feedback path uses a simple capacitor without active amplifying stages, while the error amplifier handles the comparison and error signal generation. This segmentation prevents noise accumulation that would occur in multi-stage amplifiers.
Solution Approach 2:
The patent uses a simplified copy of the feedback path that avoids complex multi-stage amplification. Instead of replicating multiple amplifier stages, a single error amplifier with a capacitive feedback path is used, which copies the essential voltage regulation function without the noise-generating multi-stage architecture.
4Reliability
If feedback resistors are removed to maximize feedback gain, then unity feedback gain is achieved, but noise from additional amplifiers increases
Solution Approach 1:
The patent extracts and removes the feedback resistors from the circuit. By eliminating the resistive feedback path, unity feedback gain is achieved without the need for additional amplifiers or resistor networks that would generate noise.
Solution Approach 2:
The patent introduces a capacitor as an intermediary element to replace the feedback resistors. This capacitor enables unity feedback gain while avoiding the noise generation associated with additional amplifiers and resistor networks.
Data Source
AI summary
According to an aspect a low noise electronic voltage regulator comprises a regulating transistor operative to regulate an input DC voltage to provide a regulated DC output voltage, an error amplifier configured to generate an error signal based on a reference voltage and a feedback voltage, wherein the error amplifier receiving the feedback voltage through a feedback loop formed between the regulated DC output voltage and the feedback voltage, and a first amplifier in the feedback loop providing a gain of greater than unity from the regulated DC output voltage and the feedback voltage.