Bandgap Reference Circuit with Isolated Current Mirror Accuracy
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Solution Overview
Problem
Conventional reference voltage generating circuits face accuracy issues due to high reference voltages affecting the drain-to-source voltage of MOSFETs, leading to inaccurate mirrored currents and reference voltages.
Innovation Solution
A reference voltage generating circuit comprising a bandgap reference voltage generator, voltage controlled current source, current mirror, input voltage generator, and voltage controlled voltage source, which employs voltage-to-current and voltage-to-voltage conversions to maintain accurate mirrored currents and reference voltages, independent of the reference voltage's impact on the operating region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the reference voltage is generated using the conventional method with mirrored current and reference resistor, then the reference voltage can be generated, but the high reference voltage affects the drain-to-source voltage of MOSFET, causing inaccurate mirrored current and lowering reference voltage accuracy
Solution Approach 1:
The patent divides the reference voltage generation into two independent stages: first generating an intermediate reference voltage using the bandgap circuit and current mirror, then using a separate voltage-controlled voltage source circuit to generate the final reference voltage. This segmentation isolates the MOSFET operating point from the final reference voltage, eliminating the harmful feedback effect while maintaining accuracy.
Solution Approach 2:
The patent introduces an intermediate reference voltage as a mediator between the bandgap circuit and the final reference voltage output. The intermediate voltage controls the voltage-controlled voltage source circuit, which then generates the final reference voltage. This intermediary structure allows the final reference voltage to be high without directly affecting the MOSFET operating point in the bandgap circuit.
2Adaptability or versatility
If the reference voltage is increased to expand output range, then higher reference voltage can be achieved, but the MOSFET operating point becomes inaccurate, reducing mirrored current precision
Solution Approach 1:
The patent segments the voltage generation function so that the bandgap circuit generates an intermediate voltage while a separate voltage-controlled voltage source circuit generates the final high reference voltage. This allows the output range to be expanded without compromising the precision of the current mirror, as the two functions are decoupled.
Solution Approach 2:
The intermediate reference voltage serves as an intermediary that controls the voltage-controlled voltage source circuit. This allows the final reference voltage to be adjusted over a wide range while the intermediate voltage remains stable and accurate, preserving mirrored current precision regardless of the final output level.
3Device complexity
If the conventional reference voltage generation circuit is used, then the circuit structure is simple, but the reference voltage accuracy is compromised due to the interaction between reference voltage and MOSFET operating point
Solution Approach 1:
The patent introduces a voltage-controlled voltage source circuit as a separate functional block, dividing the reference voltage generation into distinct stages. While this increases circuit complexity slightly, it dramatically improves reference voltage accuracy by eliminating the harmful interaction between the reference voltage and MOSFET operating point.
Solution Approach 2:
The voltage-controlled voltage source circuit acts as an intermediary stage between the bandgap reference and the final output. This additional circuit block provides isolation and control, ensuring that the final reference voltage accuracy is not compromised by interactions with the MOSFET operating point, despite the increased structural complexity.
Data Source
AI summary
Disclosed is a reference voltage generating circuit including a bandgap reference voltage generating circuit, a voltage controlled current source circuit, a current mirror circuit, an input voltage generating circuit, and a voltage controlled voltage source circuit. The bandgap reference voltage generating circuit generates a bandgap reference voltage. The voltage controlled current source circuit generates a reference current according to the bandgap reference voltage. The current mirror circuit generates a mirrored current according to the reference current. The input voltage generating circuit determines an input voltage according to the mirrored current. The voltage controlled voltage source circuit generates a reference voltage according to the input voltage. Accordingly, the reference voltage is generated with voltage-to-current conversion and voltage-to-voltage conversion so that the mirrored current can be accurate without being affected by the reference voltage and the reference voltage itself can be accurate.