V-I Characteristics (Linear and Non-Linear)

Introduction

We all know V-I characteristics as they represent the voltage and current characteristics. The V-I characteristics are used to know about the resistance and break down in electronic components and provide the operating region of a component. There are two types of V-I characteristics, i.e. linear and nonlinear. Ohm’s law exists for linear, but it is not valid for nonlinear. Ohm’s law is applicable for many materials, but it is not applicable for some materials. When the law of proportionality does not work, then ohm’s law is invalid. So, let us understand, in detail, the V-I characteristics of linear nonlinear, V-I characteristics of LED, V-I characteristics of Zener diodes, and V-I characteristics of PN junction diodes.

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What are V-I characteristics?

In terms of V-I traits, The voltage and current characteristics of any device or electrical component are denoted by the letters V-I. The V-I characteristics graph shows the change occurring in one when the change is done on the other one. The slope of the graph shows resistance, only when the slope is linear. The voltage, V, is on the X-axis, and the Current, I, is on the Y-axis in V-I characteristics. Because it is easier to control voltage rather than current, it makes the voltage the independent variable, and thus it is traditionally placed on the X-axis. 

Types of V-I characteristics 

1. Linear V-I characteristics  
2. Nonlinear V-I characteristics

Linear V-I characteristics  

Ohmic resistor shows the linear V-I characteristics. Ohm’s law tells the relation between voltage and current, where it states that the voltage and current are directly proportional to each other. Hence, a straight line is obtained when the graph is drawn. Therefore the slope of the line gives resistance. Higher the slope, the higher the resistance. 

The V-I characteristics give a straight line passing through the origin. In resistance, the current will start to flow in the opposite direction with equal magnitude if the voltage is reversed. 

Nonlinear V-I characteristics

In nonlinear V-I characteristics, resistance shows different properties. When the resistance is not constant, the V-I characteristics are not linear, depending on voltage or current. The non-ohmic resistor shows the nonlinear V-I characteristics. For example, diodes, transistors, and SCR (silicon-controlled resistors). More than one value of voltage can be obtained for one value of current because the relationship between V and I is not unique. V-I relationship depends on V. If the voltage is reversed without changing the magnitude, the current will also become the opposite. Still, the current magnitude will change, and the voltage is no longer proportional to the current. 

V-I characteristics of Zener diode

In the V-I characteristics of Zener diodes, when the forward-biased voltage is applied, it acts as a normal diode. But when the reverse-biased voltage is applied to the Zener diode, it works differently. Zener diodes work in the Zener breakdown region. Zener breakdown occurs at low reverse voltage if the diode is heavily doped. On the other hand, Zener breakdown occurs at high reverse voltage if the diode is heavily doped. Diodes act like p-n junction diodes when they are forward biased. They have a fragile depletion region because they are heavily doped and allow more electric current than a regular p-n junction diode. 

V-I characteristics of PN junction diode

In the p-n junction, the p side has an excess of holes, and hence, has a positive side of semiconductor. N side has an excess of electrons and, therefore, has a negative side. In semiconductors, the p-n junction is developed by doping. Doping means adding the impurities in semiconductors. There are three biasing conditions in the p-n junction diode.

1. Zero bias
2. Forward bias
3. Reverse bias

In forward bias, p-type is connected to the positive terminal, and n-type is connected to the battery’s negative terminal. There is a reduction in the potential barrier. When 0.3V is the voltage for germanium diodes and when 0.7V is the voltage for silicon diodes, the potential barrier decreases and there is a current flow. 

In reverse bias, The potential barrier and resistance increase. The minority carriers are present in the junction and create reverse saturation current flowing in the beginning. 

There is an increase in kinetic energy when the applied voltage increases rapidly due to minority charge carriers and affects the majority charges. In this stage, the diode breaks down, or the voltage is known as the breakdown voltage.

 V-I characteristics of LED

We all know that LED stands for light-emitting diode and is also a semiconductor device, and when current is passed through it, it emits light. LEDs are used in all semiconductor diodes and are always connected as forward bias. V-I characteristics of LEDs are similar to diodes connected in forward biased conditions. When connected in forward-biased conditions, they can emit visible light or infrared. Therefore LEDs can convert electrical energy to light energy. 

Conclusion

As we have discussed in the article about the V-I characteristics of linear and nonlinear, V-I characteristics of Zener diode, V-I characteristics of LED, V-I characteristics of PN junction diode. Some more semiconductors have V-I characteristics like SCR (silicon controlled resistors) and MOSFET (metal oxide semiconductor field-effect transistors). The resistance of a conductor is represented by the slope of the V-I graph. We can easily understand the parameters of a device by using the V-I characteristics. The V-I characteristics of semiconductors show the relation between voltage and current. To measure this, V-I characteristics are used.