Diode vs Transistor: Difference and Comparison

Key Takeaways

  1. Function: Diodes allow current flow in one direction, while transistors amplify and switch electronic signals.
  2. Structure and Operation: Diodes have a PN junction and block reverse current, while transistors have three layers and control current based on input signals.
  3. Applications: Diodes are used for rectification and signal modulation, while transistors are versatile components for amplification, switching, and digital logic.

What is Diode?

A diode is electrical equipment with two terminals that allow the current to pass in a single direction and block the other direction. It is an example of a semiconductor comprising p-type and n-type materials, forming a p-n junction.


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The diode shows two conditions – a forward biased in which the applied voltage on the anode terminal is greater than the applied voltage on its cathode. In this condition, current flows with low resistance. The second condition is – reverse biased, in which the voltage on the cathode terminal is greater than on its anode terminal. The current flow gets blocked in this situation, and the diode works as an open circuit.

Their common application of usage is it helps in voltage regulation, signal modulation, and power supplies.

What is Transistor?

A transistor is an electrical equipment with three terminal that helps in amplifying the current or switches the power and electrical signals. A transistor is designed in such a way that it has three coatings or layering of semiconductor material. The material is doped with other materials to form p-type (positive) or n-type (negative) regions.

Two main types of transistors exist: Field-effect transistors (FETs) and Bipolar junction transistors (BJTs). Within the two types, the structure of the transistor is different; that is Bipolar junction transistor has three layered semiconductors, while a Field-effect transistor has two layered semiconductors.

A transistor shows a high current gain and a voltage drop that varies with bias voltage and type.

Their common application of usage is it helps in voltage regulation, switching, and amplification. Also, in oscillators, sensor circuits, radio frequency circuits, etc.

Difference Between Diode and Transistor

  1. The function of a diode is to pass current in a single direction generally. In contrast, a transistor has a function to switch the current. 
  2. Three types of diodes are – LED, Zener, and Rectifier, while comparatively, on the other hand, a transistor has two types: Field–effect transistor and bipolar junction transistor.
  3. The structure of a diode is such a way it has a two-layered semiconductor, while the structure of a transistor has a three-layered semiconductor.
  4. A diode passes current when it is forward-biased, whereas, in contrast, a transistor amplifies the current when it is in a biased condition.
  5. A diode shows no current gain, while on the other hand, a transistor indicates a high current gain.
  6. A diode shows a voltage drop and varies with the current and the type, while a transistor shows a voltage drop when it varies with the bias voltage and type.
  7. The price range of a diode is cheap; contrastingly, a transistor shows a price range from cheap to expensive.
  8. A diode is used in voltage regulation, signal modulation, and power supplies, while comparatively, on the other hand, a transistor is used in voltage regulation, switching, and amplification. 

Comparison Between Diode and Transistor

Parameter of ComparisonDiodeTransistor
FunctionCurrent passes in one directionIt switches the current
TypesLED, Zener, and RectifierField-effect transistor and bipolar junction transistor
StructureIt is a two-layered semiconductorIt is a three-layered semiconductor
OperationCurrent is passed when in forward biasedThe current is amplified when biased
Current GainNo effectHigh current gain
Voltage DropIt varies with the current and typeIt varies with the bias voltage and type
CostCheapCheap to expensive
ApplicationsIt helps in voltage regulation, signal modulation, and power suppliesIt helps in voltage regulation, switching, and amplification
  1. https://www.sciencedirect.com/science/article/abs/pii/S0079610713000941
  2. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.140405
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