Voltage Regulator Circuit with Dual Differential Amplifiers
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing voltage regulators exhibit large fluctuations in limited current due to variations in the threshold voltage, leading to significant fluctuations in output current, typically around ±16.7%.
Innovation Solution
A voltage regulator design incorporating a first and second differential amplifier circuit, a transistor with a common gate, and a voltage generating unit to form a negative feedback circuit, where the limited current is primarily dependent on the reference voltage, allowing for the use of a stable reference voltage source like a bandgap voltage source to minimize fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple overcurrent protection circuit using a single differential amplifier and transistor is used, then the device complexity is low, but the limited current fluctuates significantly (±16.7%) due to threshold voltage variations
Solution Approach 1:
The single differential amplifier is divided into two separate differential amplifiers (first and second). The first differential amplifier compares the output voltage with reference voltage, while the second compares the voltages from the first amplifier and the voltage generating unit. This segmentation allows each amplifier to perform a specific function, reducing the impact of threshold voltage variations on the overall limited current stability.
Solution Approach 2:
A voltage generating unit is introduced as an intermediary component between the transistor and the second differential amplifier. This unit generates a voltage that is proportional to the drain current, which then serves as one input to the second differential amplifier. This intermediary voltage allows the circuit to sense and regulate the current more accurately, reducing fluctuations caused by transistor threshold voltage variations.
2Device complexity
If the limited current is determined by transistor threshold voltage, then the circuit structure is simple, but the output current fluctuates significantly (±16.7%)
Solution Approach 1:
The circuit implements a dual-loop feedback mechanism. The first differential amplifier provides feedback by comparing the output voltage with the reference voltage, while the second differential amplifier provides current feedback by comparing the voltage from the first amplifier with the voltage generated by the voltage generating unit (which is proportional to the drain current). This feedback structure allows the circuit to automatically adjust and maintain precise output current, reducing manufacturing precision issues caused by transistor parameter variations.
Solution Approach 2:
The invention changes the parameter used for current sensing from direct transistor threshold voltage to a voltage proportional to drain current (generated by the voltage generating unit). This parameter change transforms the limited current determination from being threshold-voltage-dependent to being reference-voltage-dependent, significantly improving output current precision since reference voltages can be made much more stable than transistor threshold voltages.
3Reliability
If a stable reference voltage source like bandgap voltage source is used, then the limited current stability improves (±3%), but the device complexity increases
Solution Approach 1:
The circuit is segmented into two differential amplifiers and a voltage generating unit, where each component has a dedicated function. This segmentation makes the overall complex structure more manageable and modular, allowing the benefits of using a stable reference voltage source to be achieved while organizing the complexity into functional blocks that can be independently optimized and implemented.
Data Source
AI summary
Provided is a voltage regulator capable of suppressing fluctuation in a limited current. The voltage regulator includes: a first differential amplifier circuit configured to compare a voltage based on an output voltage and a reference voltage to each other, to thereby output a first voltage; a second differential amplifier circuit configured to compare the first voltage and a second voltage to each other, to thereby output a third voltage; a first transistor configured to receive the third voltage at a gate thereof such that the output voltage is generated at a drain thereof; a second transistor, which includes a gate connected in common to the gate of the first transistor and has a predetermined size ratio to the first transistor; and a voltage generating unit, which includes one end connected to a drain of the second transistor and is configured to generate the second voltage at the one end.