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Voltage References
Voltage Reference Solutions
National Semiconductor has led the industry in voltage references (Vrefs) for 40 years, beginning with the LM100. Industry standard references such as the LM431, LM385, and LM336 voltage references have become industry classics and National's leading voltage regulator portfolio is due in part to its expertise in voltage references.
National's reference portfolio features low temperature coefficient and precise initial accuracy voltage references. Both series references and shunt references are available for a wide variety of applications, including high precision references for data converters and low noise references for sensor conditioning. Voltage references are also commonly used as voltage monitors, current limiters, and programmable current sources.
A series reference is an excellent choice where low power dissipation is required. A shutdown or power-saving mode is possible with series references. National offers series references with temperature coefficients (tempcos) down to 3ppm and 0.05% initial accuracy. Some of National's featured series references are shown below.
A series reference is the right choice for providing an accurate reference to any precision data converter with an external reference pin. Beyond 8 to 10 bits of resolution, most data converters will require an external reference to ensure that the converter's intended precision can be achieved. Selecting the right voltage reference with the appropriate temperature coefficient, as well as load and line regulation, enables accurate data conversion. National's LM4140 ultra low noise, high precision voltage reference is an excellent match for a high resolution ADC or DAC in such applications as test and measurement equipment, industrial process control, data acquisition systems, medical equipment, or precision scales.
Bridge Sensor Reference
Another common application of the series voltage reference is sensor conditioning. As shown here, a high precision voltage reference is useful in bridge sensor applications. These low noise series voltage references pair well with National's precision amplifiers to provide an analog solution for an array of sensor applications. An accurate, low noise voltage reference, such as the LM4132, enables high precision sensing for other sensing applications such as thermocouples, thermopiles, and pH sensors.
Shunt References
National offers a range of precision shunt voltage references, which are great for applications requiring better performance than a zener diode can provide. Shunt regulators have the benefit of no input voltage max and excellent supply rejection (PSRR). They can be used to create negative or floating reference voltages. A list of featured shunt references is shown below.
