Voltage reference sources, power shunt voltage references and stabilizers
In order to generate a reference voltage level independent of the supply voltage, we will need a dedicated system. Such a circuit is the power shunt voltage reference. Such components are very commonly used in analog electronics and mixed analog-to-digital systems such as regulators, drivers, and analog-to-digital and digital-to-analog converters. Voltage references work in such a way that they use a reference voltage to compare with other voltages or to convert a given analog voltage from and to a digital form.
A very common mistake is to identify two completely different devices with each other: voltage stabilizers (linear and impulse) and voltage references. It is particularly easy to get confused when both devices output a certain voltage, regardless of the supply voltage. However, they are much more different than you might think. First of all, the voltage patterns are much more accurate and stable, and also have a lower output current, which means that the reference voltage from such a circuit often has to be buffered, for example using an op-amp.
How to stabilize the reference voltage?
Voltage reference stabilization is a key element in the field of electronics and electromechanics. There are many different methods (physical phenomena) that are used to construct voltage patterns.
The first sources of reference voltage were electrochemical processes, however such devices are highly impractical and cannot be used outside the laboratory. The next generations of reference voltage stabilizing systems were based on gassed lamps. The introduction of semiconductor systems closer to us historically was the next stage in the development of voltage patterns. It was this stage that brought us the closest to the technological state we are in now.
Chronologically, the Zener diodes were the first. Currently, however, the most commonly used systems are based on the sum of the voltage drop across a semiconductor diode and the voltage difference across two PN junctions with different values of the flowing current. This solution offers high temperature stability. This is due to the fact that the used effects have negative and positive temperature coefficient, respectively, thus compensating for each other.
Analog and hybrid systems
A typical application of reference voltages are mixed (hybrid) systems, i.e. analog-to-digital. These systems use the level of this voltage in the systems responsible for the translation of analog values into digital. All amplitude values are dimensionless in the digital domain. Only at the moment of translation from or to analog value they are being converted to some fraction of the full scale voltage of the given circuit. Most often this voltage is equal to the voltage derived from the voltage standard.
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