Relay vs Transistor-Difference between Relay and Transistor
This page compares Relay vs Transistor and mentions difference between Relay and Transistor.
What is Relay?
• The relay is controlled device which opens and closes contacts in order to effect
operation of other devices in the same or another electric circuit.
• The relay is used in circuits with lower ampere capacity i.e. Max. 20A.
• They are smaller in size.
• They have at least two NO/NC contacts.
• They are used in control circuits, automation circuits, protection circuits and switching circuits.
What is Transistor?
• There are two types of transistors viz. NPN and PNP. It can be used as amplifier as well as switch.
• The terminals of transistors are known as Base, Emitter and Collector.
• Transistor can function as switch. There are two modes in a transistor cut-off and saturation. In cut-off mode, transistor is said to be open switch. In saturation mode, it is said to be closed switch.
• In NPN, when negative DC bias voltage is applied to base, it operates in cut-off mode and when positive voltage is applied to base, it operates in saturation mode.
• Refer Application Note on Transistor as switch >>.
Following table mentions difference between relay and transistor.
|Power supply||It can work with AC and DC.||It can work with DC only.|
|Power loss||It has zero closed resistance.||It has forward voltage drop. Due to this reason, lots of power gets wasted.|
|Resistance||Relay has infinite open resistance.||Transistor has leakage which can affect attached electronic circuits.|
|Temperature||Relay can operate at extreme temperatures.||Transistor can operate upto 95oC and little below 0oC.|
|Speed of operation||Relay is much slower and operates at 200 Hz speed.||Transistor can operate at MHz speed.|
|Damaged by||Relay is primarily damaged due to over current.||Transistor is damaged due to voltage peaking, over current etc.|
|Isolation||It has very high isolation from control coil.||It is not isolated from Base, Gate or Trigger.|
|Wear out||It has much shorter mechanical wear out contact life.||Transistor switches almost never wear out.|
|Application||It can used only to open and close circuits.||Transistor can amplify analog signals as well as functions as switch.|
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