Analog Electronics, Diode, Electronics, Transistor

Difference Between Diode and Transistor, Diode Vs Transistor

Difference Between Diode and Transistor

Difference between Diode and Transistor is very important to understand because diode and transistor are considered as the heart of the electronic circuit. The major difference between diode and transistor is that a diode is a current controlling device which allows the current in only one direction it has two terminals and it is mostly used for converting AC into pulsating DC.

On the other hand, A transistor is a three terminal device which allows the current form high resistance to low resistance region. The word transistor is composed of two words. 1: Transfer 2: Resistor. Thus, it is a device which transfers the resistance between input low resistance region to output high resistance region.

There are many differences between Diode and Transistor w.r.t their symbols, construction, operation, applications, and in this post, we will cover them one by one.

Difference Between Diode and Transistor Comparison Chart

Definition Diode is a semiconductor device which allow current in only one direction.Transistor is a semiconductor device which transfers input signal of low resistance to output high resistance.
SymbolDiode symbol (2018)transistor symbol (2018)
TerminalsDiode is two terminal device (Anode (-), Cathode (+))Transistor is three terminal device (Base, Emitter, and Collector)
TypesDiode is classified in many types such as Zener Diode, Tunnel Diode, LED, Varactor Diode, Photodiode, Gunn Diode, Shcottkey Diode, .etc.Transistor is classified into two types: BJT Transistor and FET (Field Effect Transistor).
ConstructionDiode is formed when P-type material is joined with N-type material.Transistor is formed when Two same layer are joined together with alternative layers in between (N-P-N or P-N-P)
OperationDiode has two mode of operation. When Diode is forward bias it act as ON Switch and when diode is reverse biased it act as OFF SwitchTransistor has three mode of operations.
Active mode: (it act as Amplifier).
Saturation mode: (It act as ON Switch).
Cutt off mode: (It act as OFF Switch)
DeviceDiode is Uncontrolled device.Transistor is Controlled device. (output current can be controlled by varying voltages at base terminal).
Depletion RegionDiode has one depletion region (PN-region)Transistor has two depletion regions (PN and NP combined).
ApplicationsDiode is used in rectification, Clipping, Clamping, Voltage Multipliers, Power supplies, Protection Circuits .etc.Transistor is used for Switching and Amplification Purpose.



A Diode is a two terminal semiconductor device which is formed when a P-type semiconductor and an N-type semiconductor is combined together. The junction formed by joining these two semiconductors is known as PN junction and a simple PN junction is also called as Diode. The diode is the most widely used electronic component which is almost used in every electronic circuit. It is used to provide AC conversion into Pulsating DC.

diode construction

Operation of a diode is simple when the PN junction is forward bias with the external bias battery the diode allows the flow of current and when the PN junction is reverse biased the diode does not allow the flow of current just like an open switch.

By connecting a Positive terminal of the battery with P-type material and a Negative terminal of the battery with N-type material PN junction can be made forward bias, this is the condition where a diode is mostly operated.

By connecting the Negative terminal of the battery with P-type material and Positive terminal with N-type material diode is made reverse bias.


A Back-to-Back connection of two diode forms the transistor, a transistor is a three terminal device, and three terminals of a transistor are Emitter, Base, and Collector. There are two junctions in the transistor Base-Emitter junction and Base-Collector junction. A transistor is capable of performing the operation of Switching and Amplification.

transistor construction

There are three operation modes of transistor commonly known as an Active region, Cut-off region, and Saturation region.

In Active region one junction is forward bias and one junction is reverse biased and transistor behaves as an amplifier, in the active region of transistor week signal is applied at the input and strong signal is achieved at the output.

In the saturation region, both junctions of a transistor are forward bias and the transistor behaves as a closed switch.

In Cut-off region, both junctions are reverse biased and transistor behaves as an open switch.

Key Differences

  1. One of the big difference between diode and transistor w.r.t their terminals is that diode has two terminal (anode and cathode) whereas transistor has three terminals (Emitter, Base, and Collector).
  2. A diode is consist of one depletion region, whereas a transistor has two depletion regions
  3. In terms of their application diode is used for switching whereas a transistor is used for switching as well as amplification.
  4. In terms of their bias, the diode needs only one bias battery to operate whereas transistor utilizes two bias batteries for the operation.
  5. In terms of their working, the diode is the current controlling device it allows the current to flow in one direction whereas the transistor is a device which transfers the resistance between low resistance to high resistance region.
  6. The diode is formed from PN junction whereas a transistor is formed from two back to back connections of diodes.
  7. The diode is classified into different types such as Zener diode, Varactor Diode, Tunnel Diode, Light emitting diode, Photodiode, Gunn Diode, etc. whereas a transistor has only two types BJT (Bipolar junction transistor) and FET (Field Effect Transistor).
  8. In terms of their construction, a diode has two regions P-region and N-region, P-region is consist of holes in majority whereas N-region is consist of Electrons in a majority
  9. On the other hands, a transistor has three regions, Emitter region, Base region, and Collector region. The Base region have very less area, the collector region has a larger area whereas the emitter region has a moderate area.
  10. The diode is utilized in Switching operations, Clipping circuit, clamper circuits, voltage multipliers, rectifiers, whereas a transistor is utilized for switching operations, amplification of audio signals, amplification of current or voltage signals.


The diode is a two-terminal device which allows current to flow in one direction while the transistor is a three terminal device which passes current from input low resistance region to output high resistance region via the base. A diode is used in various applications of electronics such as in rectification circuit, clipper, clamper, voltage multiplier, Power supplies, protection circuits, and switches etc.

A diode has two modes of operation and it is similar to a switch. it behaves as ON switch when it is forward bias, and it behaves as OFF Switch when it is reversed biased. Transistor can act as an Amplifier and a Switch, this application creates a major difference between Diode and transistor. Diodes are classified into many different types such as Zener Diode, Tunnel Diode, Varactor diode, Photodiode, Light Emitting Diode, PIN Diode, Gunn Diode, Schottky Diode, etc whereas Transistor is classified into two types Bipolar Junction Transistor and Field Effect Transistor.

It is considered that the diode is simple PN Junction whereas Transistor has two PN junction is formed by connecting back to back diodes.

Related Topics:

  1. Difference Between Clipper and Clamper Diode
  2. Difference Between NPN and PNP Transistor

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: