V-I Characteristics

The voltage-current characteristics of an electrical component or device are referred to as V-I characteristics. The V-I graph provides information about resistance and breaks down an electronic component. It also specifies a component's operating region. By studying its characteristics, we can learn where and how to use a component in an electric circuit.

An electronic component's voltage-current characteristics describe its behaviour for various applied voltage values. Simply put, it is the graph obtained when current is measured through an electronic component while a voltage is applied across it. Because it is easier to control the applied voltage rather than the current. In V-I characteristics, the voltage is considered the independent variable.

Linear VI Characteristics

Ohmic resistors display linear V-I properties. Ohm's law discusses the relationship between voltage and current, stating that voltage and current are proportional to each other, resulting in a straight line when a graph is drawn. The line's slope provides resistance. The greater the slope, the greater the resistance.

Hence,

$R=\dfrac {\Delta V}{\Delta I}~and~R=\tan q$

The V-I properties result in a straight line going through the origin. If the voltage polarity is switched in a resistor, the current will begin to flow in the other direction with equal magnitude if the magnitude of the voltage is not changed.

Linear VI Characteristics

Non-linear V-I Characteristics

If non-linear V-I characteristics exist, as they do, resistance must have a different property. If the V-I graph is not linear, the resistance is not constant and depends on either voltage or current. Diodes, SCRs (Silicon controlled resistors), transistors, and other non-ohmic resistance devices are examples. These are the most noticeable changes in non-linear graphs.

• Voltage and current are no longer proportional.

• Voltage determines the relationship between voltage and current when the voltage is reversed without changing the magnitude, the current reverses but the magnitude changes.

• Because the relationship between V and I is not unique, more than one voltage value can be obtained for a given value of current.

Non-Linear VI Characteristics

V-I Characteristics of SCR

The SCR (Silicon Controlled Rectifier) V-I Characteristics is a graphical representation of current through the SCR and voltage across the anode to cathode terminal. SCRs are three-terminal semiconductor switching devices that regulate and invert power flows. Based on its V-I characteristics, an SCR has three primary modes of operation: reverse blocking mode, forward blocking mode, and forward conduction mode. SCRs are also known as thyristors or thyroid transistors.

V-I Characteristics of SCR

V-I Characteristics of MOSFET

MOSFET is an abbreviation for Metal Oxide Semiconductor Field Effect Transistor.

It is a three-terminal device with a voltage output that regulates current flow between the output terminals, source, and drain. So they have drain (D), source (S), and gate (G) terminals, with a substrate (S) as the fourth terminal. The two types of power MOSFETs are depletion-type transistors and enhancement-type transistors.

V-I Characteristics of MOSFET

V-I Characteristics of LED

LED is an abbreviation for light-emitting diode, which is used in all types of semiconductor diodes with electrical properties similar to a PN junction diode.

The LED V-I characteristic is as follows:

V-I Characteristics of LED

V-I Characteristics of PN Junction Diode

A PN junction diode is formed when an N-type material is fused with a P-type material to form a semiconductor diode. When an N-type material (which has more free electrons) is fused with a P-type material (which has more holes) to form a semiconductor diode. There are three types of biassing conditions:

• Zero bias

• Forward bias
  

• Reverse bias

The graph below depicts the p-n junction diode's V-I characteristics curve.

V-I Characteristics of PN Junction Diode

V-I Characteristics of Zener Diode

A Zener diode is an electronic device that operates in the Zener breakdown region. When these diodes are forward-biassed, they behave similarly to p-n junction diodes. Because they are heavily doped, these diodes have a very thin depletion region and can carry more electric current than regular p-n junction diodes.

The V-I characteristic of the Zener diode is given below:

V-I Characteristics of Zener Diode

V-I Characteristics of Photodiode

The photodiode operates in reverse bias mode. Reverse voltages are plotted in volts along the X axis, and reverse currents are plotted in microamperes along the Y axis. Reverse current is independent of reverse voltage. When there is no light illumination, reverse current is almost non-existent. "Dark current" is the smallest amount of current present. When the brightness of the light increases, so does the reverse current.

V-I Characteristics of Photodiode

V-I Characteristics of BJT

The VI characteristics of a power BJT differ from those of a signal-level transistor. The main distinctions are the quasi-saturation region and the secondary breakdown region. The device operation at the primary and secondary breakdown regions should be avoided because it will result in the device failing catastrophically.

V-I Characteristics of BJT

Solved Problems

1. A transistor has a current gain of 30 Ampere. If the collector resistance is 6 kΩ, and the input resistance is 1 kΩ, calculate its voltage gain.

Solution:

Given,

${{R}_{in}}$ =1 kilo ohms and ${{R}_{out}}$ = 6 kilo ohms

${{R}_{gain}}$ = ${\dfrac{{R}_{out}}{{R}_{in}}}$ = ${\dfrac{{6}}{{1}}}$ = 6

Voltage gain = current gain $\times$ Resistance gain = 30 $\times$ 6 =180

2. A battery of 10 Volts connected to a conductor induces a current of 10 mA in the conductor. Find the resistance of the conductor.

Solution:

The relation gives the resistance of a conductor,

R = ${\dfrac{{V}}{{I}}}$

Given:

V = 10V

I = 10mA = 0.01 A

Plugging in the values inside the relation,

R = ${\dfrac{{V}}{{I}}}$

R = ${\dfrac{{10}}{{0.01}}}$

R= 1000 ohms

Summary

V-I characteristics are the voltage or current characteristics of an electrical problem or device. The v-i graph provides useful information about the resistance and breaks down a digital component of the equation. It also serves as a workspace for an element. Reading an object's characteristics allows us to determine where and how to use it in an electric circuit. Electronic factors are distinguished by their voltage-ampere characteristics when applied to varying voltages. When a voltage is applied across an electronic component, it deviates from the graph that depicts the relationship between voltage and current when current is measured.