What Is a Voltage Reference?
A voltage reference is a special chip that produces an extremely stable and precise voltage even as temperature, load and input voltage change. It's the "accuracy anchor" of measurement.
How Does It Differ From a Regulator?
A voltage regulator is designed to supply lots of current; its accuracy is medium. A reference supplies little current but its voltage is far more precise and stable (low temperature drift).
Why Is It Needed?
An ADC compares the voltage it measures against the reference. If the reference drifts, all measurements drift. So a stable reference is essential in precise measurement.
| Property | Reference | Regulator |
|---|---|---|
| Purpose | Accurate voltage | Supplying power |
| Current | Low | High |
| Stability | Very high | Medium |
Types
There are bandgap (most common), series and shunt (zener-like) references. Precision is given as temperature drift in ppm/°C.
Where Is It Used?
ADC/DAC references, precision measurement instruments, sensor calibration, current sources and test/measurement equipment.
Main Sources of Error
A reference's accuracy is set by its initial accuracy, temperature drift (ppm/°C) and long-term drift. In precise measurement these three values should be checked from the datasheet; also, a filter capacitor at the output improves stability.
Common Mistakes
Frequently Asked Questions
What does ppm/°C mean?+
What is a bandgap reference?+
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