CMOS Voltage References: An Analytical and Practical Perspective

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Voltage Reference

A voltage reference circuit is a device that generates an exact output voltage which in theory does not depend on the operating voltage, load current, temperature, or the passage of time. Readers should not mistake voltage regulators for voltage reference circuits even though they are very similar, as both circuits generate regulated output voltages that are immune to the change in load current, input voltage, temperature, etc. A voltage regulator, however, is intended to provide a higher output current than that of a voltage reference circuit. As a result, the voltage regulator is much less accurate than a voltage reference circuit, the output noise is higher, and the long term stability is not specified. In fact, every voltage regulator requires a precise voltage reference circuit in its core.

Besides the voltage regulators, voltage reference circuits are used in all circuits that require a precise voltage for measurements to be made against. The accuracy of any measurement can be regarded as good as it is able to be compared against a known standard. High resolution A/D and D/A converters, digital meters, smart sensors, threshold detectors, servo systems, battery management systems, and many other precise industrial control systems require precise voltage reference circuits in their cores. Various circuits have been developed to provide accurate reference voltages, whereas their performance can be characterized by the objective measures detailed in the following ...