Difference between Transistor and Relay


Transistor VS Relay


The main difference between a Transistor and a Relay is transistor is a Switching cum amplifying device whereas a relay is a switching device. The transistor is a semiconductor device or can be called a passive electronic component. On the other hand, it will be better to call the relay as a device. Both are very different in construction. But in some particular applications, you will see some similarities so you may be confused about the proper distinction between them.

What is a Transistor?


The transistor is a passive electronic component built with semiconductor material. Generally, a conventional transistor has three terminals and for its operation we have to use those three terminals for both the input and output circuit by using a terminal common for both. The main function of a transistor is to amplify or switch electrical or electronic signals. The transistor performs its operation by changing its own internal physical structure.

There are so many types of transistors available such as BJT(Bipolar Junction Transistor), Field Effect Transistor(FET), etc. These two are the main two types. BJT is a current-controlled device whereas FET is a voltage-controlled device. By applying a voltage and current to one pair of terminals can control the current flow through another pair of terminals. Generally, they are mostly used to control the higher output power with lower input power. In electronics engineering, especially in digital electronics, you will see a lot of useful applications. In fact, the transistor is the basic building block of any digital circuit. I think you may get any digital circuit without any transistors.


What is a Relay?


A relay is basically an electrically controlled switch that can switch the electrical signal or power. A relay operates by making some movements. Of course, there are different types of relays that operate with different principles. A relay has a set of input terminals and single or multiple output terminals. Here, you can get a similarity between a relay and a transistor that using a relay we can control a high-power signal using low-power signals.

Although there are so many types of relay are available but you must know the difference between two important types that is a conventional electromechanical relay(EMR) and a Solid State Relay(SSR). An electromechanical relay has an electromagnetic relay and a mechanical contact mechanism. According to the presence and absence of an electric supply in that relay coil, the contact mechanism operates. On the other hand, there is no mechanical movement mechanism in a solid-state relay. It is made of semiconductor devices such as transistors.


Transistor VS Relay


The key differences between a Transistor and a Relay are,
  1. Transistors are most suitable for Direct Current(DC) applications whereas Relays are suitable for both AC and DC applications.
  2.  Transistors can be used for signal amplification but a relay is not suitable for signal amplification.
  3. A relay(especially an electromagnetic relay) can consume a large amount of input current for switching whereas a transistor consumes a very low current.
  4. There is almost no latching problem in transistors whereas conventional relays have latching problems.
  5. Of course, a transistor has a very fast switching speed whereas a relay has a poor switching speed.
  6. In the case of a relay, you will get higher isolation between the input and output circuit but in the case of a transistor, the input and output circuit may not be strongly isolated.


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Difference between Transistor and Relay Difference between Transistor and Relay Reviewed by Author on 10/29/2022 Rating: 5