Voltage Current Characteristic of Diode [Updated in 2026]

Hello, fellows, I hope all of you are enjoying your life. In today’s tutorial, we will have a look at the voltage-current characteristics of a diode. The diode is a 2-terminal semiconductor device that is used to rectify alternating current into direct current. If it converts a half-wave of alternating current into direct, then this process is called half-wave rectification. If you convert both parts of alternating current into direct current, this process is known as full-wave rectification. In almost every electronic device and engineering project, a diode is used, such as UPS and some other electronic projects. There are different types of a diode according to their construction and working, such as LED, OLED, Zener, etc.

There are normally 2 methods used to provide input supply to the diode. The first is forward biasing, and the second is reverse biasing. If the positive terminal of the battery is connected with the anode and the negative terminal is connected with the cathode, this type of bias is known as forward bias. If the negative terminal of the battery is connected with the anode of the diode and the positive is connected with the cathode, this is called reverse biasing. By using these to bias, we will discuss the effect of current and voltage across the diode and find different characteristics. So let’s get started with the voltage-current characteristic of the diode.

Voltage Current Characteristic of Diode

• For a practical understanding of V-I characteristic of a diode, we discuss the forward biasing and reverse biasing conditions one by one.

V-I Characteristic for Forward Bias

Note: In this post, there are 2 types of voltage that will be discussed. The first one is forward biased voltage, and the second is forward voltage (VF). The difference is that forward-biased voltage across the complete circuit is provided by the external voltage source. While forward voltage (VF) is the only value of voltage across the diode in a circuit. Let’s start.

• The current that flows when the diode is forward is called forward current. In the given figure this current is denoted as IF.

• In the given figure, there are 2 circuits shown for forward-biased arrangements

• In this circuit, we will increase the value of voltage from 0 across the diode and will find the effect on it.

• In the circuit, resistance is connected in series; it is used to limit the value of current passing through the circuit to save a value that will not damage the diode.

• At the start, there is no voltage across the diode. As we increase the forward-biassed voltage value, the current IF and voltage across the diode increase. The value of forward current and voltage across the diode can be seen in an ammeter and voltmeter connected in a circuit.

• This arrangement is shown in the above circuit denoted as ‘a’.

• Some value of forward biassed voltage is lost across the limiting resistance.

• In the above figure, the circuit denoted as ‘b’ explains the condition when the value of forward biassed voltage is such that the voltage across the diode is almost 0.7 volts or the potential barrier, while the increment in value of forward current is very fast.

• As we continuously increase the forward-biassed voltage-current, it also increases very fast with the forward-biassed voltage, but the voltage about the dido increases very slowly after the 0.7 volts that are potential barriers.

• The less increment in the voltage across the diode after 0.7 volts is due to the voltage loss across the internal resistance of the semiconductor material by which the diode is constructed.

V-I characteristic curve for a forward-biased diode

• If the above circuit measurements on the graph this graphical representation is called the V-I characteristic curve for a forward-biased diode.
• In the figure below this graphical representation is shown.

• You can see in the graph that is denoted as a that VF forward voltage, or voltage across the diode, is along the x-axis and (IF) forward current is along the y-axis.

• In the graph (a) you can see that there is very little increment in the forward current (IF) till the value of forward voltage is 0.7 volts.

• After the 0.7 volts of forward voltage, the increment in the forward current is very fast, and (VF) is almost constant.

• The increment in forward voltage is less due to internal resistance or dynamic resistance voltage drop, and forward continuously increases.

• In the curve (a) you can see three different points, A, B, and C.  The first point, ‘A,’ explains the zero biasing condition.

• ‘B’ is a point where the value of forward voltage, or VF, is less than the potential barrier, or 0.7 volts.

• While point ‘C’ defines the position where the forward voltage equals the potential barrier or 0.7 volts.

• After point C, or the knee of the curve, the increment in forward current is large, while the increment in forward voltage is minor.

• In practice, the value or forward voltage is almost one volt according to the value of forward current.

Dynamic Resistance

• The given figure is the expended form of V-I curve for forward bias diode and it explains the dynamic resistance.

• As linear resistance has a constant value, but the value of resistance offered by the diode in forward biasing does not remain the same throughout forward biasing diode.

• This resistance is known as AC resistance or dynamic resistance.

• Internal resistances of electronic components are generally labeled by lowercase italic r with a prime in its place of the R.

• The dynamic resistance of the diode before the knee of the curve is high since the increment in current is very low with the increment in the voltage.

• As the voltage approaches the knee, the curve resistance starts to decrease, and after the knee point, it becomes much less, and the current starts to increase.

V-I Characteristic of Diode for Reverse Bias

• When the diode is in a reverse-bias condition, then the current (IR) flow is very low.

• When the voltage across the diode is zero, the IR is also zero.

• With an increase in reverse-biased voltage, then a very small value of reverse current flows through the diode, and the voltage across the diode is also lower.

• If we continuously increase the applied voltage, then if the value of reverse voltage across the diode is equal to the breakdown voltage (VBR), then the reverse current flows very rapidly.

• With further increase in the reverse-biased voltage, the reverse current also increases continuously, but the increase in the voltage across the diode is very small.

V-I Curve for Reverse Biased Diode

• If we make a graphical representation of reverse biasing of a diode. The curve obtained is called V-I characteristic curve for a reverse-biased diode.
• In the given figure, you can see the graphical representation.

• In the curve, you can see that the reverse voltage (VR) across the diode is drawn on the negative X-axis and the reverse current (IR) on the negative Y-axis.

• The increment in the reverse current is very little till the point where reverse voltage is at the knee point.

• After the knee of the curve, the reverse voltage is almost the same, but the reverse current increases very fast.

• If the value of reverse current is not controlled, then it can overheat or damage the diode.

• The doping level decides the breakdown voltage of the diode; the doping level of the diode is set by the diode’s manufacturer.

• Normally a general-purpose diode has a breakdown voltage value larger than fifty volts, and some special diodes have a breakdown voltage of almost five volts only.

Complete V-I Characteristic Curve of Diode

• If we combine both forward-biased and reverse-biased curves of Dido, then we have a complete V-I characteristic curve. It is shown in the below figure.

Temperature effect on diode V-I characteristic

• If a diode is forward biased and we increase the temperature, then there will be an increment in the forward current IF at a specified value of forward voltage.
• With the increment of temperature forward voltage decreases at a certain value of current.
• The effect on the diode V-I curve is shown in the given figure.

• You can see there are 2 curves in the graph: the blue is at room temperature (25 centigrade), and the red curve is for an increment in temperature (25 °C + ΔT).
• With an increment in one degree Celsius, the potential barrier decreases by two millivolts.
• If the diode is in reverse-bias conditions, then the increment in temperature of the reverse current (IR) also increases.

What are the different types of diodes?

There are different types of diodes, like

• Silicon diodes
• Germanium diodes
• Zener diodes
• Tunnel diodes
• Light-emitting diodes (LEDs)
• Photodiodes
• Varactor diodes
• Schottky diodes

Read Also:

So friends, that is the detailed post on the Voltage-Current Characteristic of the Diode if you have any further queries, ask in the comments. Thanks for reading. See you in the next post. Have a good day.