vref

Vref, short for reference voltage, denotes a precise, stable voltage used as a reference point for measuring or converting signals in electronic systems. In analog circuits, Vref provides a fixed threshold or scaling factor for ADCs, DACs, comparators, and instrumentation amplifiers. A well-designed voltage reference is typically produced by a dedicated voltage reference circuit, often based on a bandgap reference, zener reference, or buried-zener device. Bandgap references generate about 1.2 to 1.3V with very low drift; many parts provide 2.5 V, 3.3 V, or other fixed values. Voltage references are available as fixed-value references or adjustable devices (via resistor dividers or DACs). They can be packaged as standalone ICs or integrated on a microcontroller or analog front end.

Key specifications include accuracy (initial error), temperature coefficient (ppm/°C), long-term stability, output impedance or dynamic impedance, output drive capability, line and load regulation, and noise (voltage noise density). Performance is characterized by PSRR when used in noisy supplies.

Applications: ADCs and DACs for precise conversion, reference inputs in instrumentation, precision regulators, and biasing networks. In ADCs, Vref determines full-scale range and resolution; Vref- is often connected to a common reference (ground) and Vref+ to the reference node.

Selection considerations include required accuracy and drift over temperature, supply voltage, load conditions, noise tolerance, and package or integration constraints. Proper decoupling and layout are important to minimize noise coupling into Vref.

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