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Understand the requirements and types of voltage reference circuits. Learn how to achieve stability, precision, and independence from power supply, temperature, and process variations. Explore various methods like voltage dividers, MOS diode references, and gate-source threshold voltage references.
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REFERENCE CIRCUITS A Reference Circuit is an independent voltage or current source which has a high degree of precision and stability. • Requirements of a Reference Circuit • Output voltage/current should be independent of Power Supply • Output voltage/current should be independent of temperature • Output voltage/current should be independent of process variations.
SENSITIVITY Sensitivity is a measure of dependence of Vref (Iref) upon a parameter or variable x which influences Vref (Iref). ; Where x could be VDD or temperature
TEMPERATURE DEPENDANCE Minimize the fractional Temperature Coefficient
Simple Voltage References Objective is to minimize • Types of Voltage References: • Voltage Dividers – Active • MOS Diode Reference • PN Junction Diode Reference • Gate-Source Threshold Voltage Reference • Base-Emitter Reference Circuit
By taking the derivative at T0 (assuming that JC has a temperature dependence of Tα , the dependence of VBE withtemperature is given by