Replica Transistor Voltage Regulator with Feedback Circuit
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Solution Overview
Problem
Conventional voltage regulators, including replica transistor and current conveyor designs, suffer from poor accuracy, limited power supply rejection ratio (PSRR), and large area occupancy on semiconductor substrates, making them unsuitable for many applications.
Innovation Solution
A voltage regulator architecture featuring an operational amplifier, output source follower, replica source follower, and feedback circuit with a small feedback resistor or feedback transistor, which provides accurate voltage regulation with improved PSRR and reduced area occupancy by using a leaker transistor for stability and a resistor network for current control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional replica transistor voltage regulator architecture is used, then device complexity and area occupancy are reduced, but output voltage accuracy deteriorates with variation of 7-10% or more
Solution Approach 1:
The patent introduces a feedback circuit that couples the output node to the inverting input of the operational amplifier through a feedback resistor. This feedback mechanism continuously monitors the output voltage and adjusts the control voltage to maintain accurate regulation, resolving the accuracy problem while preserving the simplicity of the replica transistor architecture.
Solution Approach 2:
The patent segments the voltage regulator into distinct functional blocks: operational amplifier, replica leg, output leg, and feedback circuit. This segmentation allows each component to be optimized independently while maintaining overall system simplicity, achieving high accuracy without excessive complexity.
2Measurement precision
If current conveyor architecture is used, then output voltage accuracy is improved to 5% variation, but area occupancy increases to 133K-150K square microns
Solution Approach 1:
The patent uses a replica leg that copies the structure and characteristics of the output leg but operates at lower current levels. This copying approach allows accurate voltage sensing and feedback without requiring the large area needed for full-scale current conveyor circuits, achieving high accuracy with compact footprint.
Solution Approach 2:
The patent introduces an operational amplifier as an intermediary element that bridges the replica leg and output leg. This intermediary provides high-gain voltage control and feedback, achieving current conveyor-level accuracy without requiring the complex current conveyor circuitry and its associated large area.
3Measurement precision
If current conveyor architecture is used, then output voltage accuracy is improved, but power supply rejection ratio deteriorates to -5 dB or greater
Solution Approach 1:
The feedback circuit continuously monitors output voltage and adjusts the control voltage to compensate for power supply variations. This negative feedback mechanism provides high power supply rejection ratio by actively counteracting noise and variations from the power supply, achieving better than -20 dB PSRR.
4Area of stationary object
If conventional replica transistor voltage regulator is used, then device area is minimized, but headroom is limited with maximum allowable shift less than 50 millivolts
Solution Approach 1:
The patent uses dynamic feedback control where the operational amplifier continuously adjusts the control voltage in response to output voltage changes. This dynamic adjustment capability allows the regulator to handle large input voltage shifts (up to 280 mV headroom) while maintaining small device area, as the control mechanism adapts rather than requiring additional headroom margin.
Data Source
AI summary
A voltage regulator is provided having high accuracy, low PSRR, and no headroom limitation. Generally, the regulator includes: an operational amplifier (OPAMP) having a non-inverting input coupled to a reference voltage; an output source follower coupled to and controlled by an output of the OPAMP, the output source follower including a drain coupled to a voltage source and a source coupled to an output-node of the regulator; a replica source follower coupled to and controlled by the OPAMP, the replica source follower including a drain coupled to the voltage source and a source coupled to circuit ground through a resistor network; and a feedback circuit extending from the output-node through a feedback resistor to the source of the replica source follower and through at least a first resistor of the resistor network to an inverting input of the OPAMP to couple a feedback voltage thereto. Other embodiments are also provided.