What is a power transistor?

The transistor is the basic block of electronics, it is a semiconductor device that handles the voltage and current variations to a proper circuit operation.

A transistor is used for switching and amplifier application at circuits, but the power transistor had the ability to handle higher power signals without damaging its whole body.

Difference between normal transistors and power transistors?

We already mentioned transistors, it is a silicon semiconductor-based device that is used to handle current and voltage quantities, but transistors are the current controlling device.

Transistors are used for switching and amplification applications, these signal variations are been applied to different circuits.

Power transistors are devices that can handle higher power values, the power transistor is mainly capable of handling higher current values.

A power transistor is just like a normal transistor but it is capable of withstanding higher power values than normal transistors, which means the power transistor component body itself is harder to withstand, and also we can easily attach heat sinks with it.

Types of power transistor

  • Bipolar Junction Transistor (BJT)
  • Metal Oxide Semiconductor Field Effect Transistor (MOSFET)
  • Insulated Gate Bipolar Transistor (IGBT)
  • Static Induction Transistor (SIT)
  • Field Effect Transistor (FET)

Symbol of the power transistor

Symbol of the power transistor
Symbol of the power transistor

The figure shows the symbol of BJT transistors such as NPN and PNP, the power transistors had the same symbol as the normal transistor.

But each power transistor type we listed above have different symbolic representations, this is because they all have different structural details and have different type of operation.

Working of the power transistor

The working of the Power transistor is the same as our normal transistor, the transistor is a three-terminal and three-layer semiconductor device that works as amplifiers and switches.

When we consider the working operation of a power transistor, the current carry capacity of the power transistor is higher than the normal transistor.

The three terminals of the transistor such as emitter, collector, and base are the connections taken out from the three layers of the transistor.

At the transistor component itself, we can categorize its terminals as input and output, the input of the transistor is between base-emitter, and output of the transistor is between base-collector, then the base terminal is the trigger of the transistor.

We already mention that transistors are commonly used for amplifiers and switching applications.

Graphical representation of power transistor

Graphical representation of power transistor
Graphical representation of power transistor


The figure shows the characteristics curve of the Power transistor, which shows three different operation regions of the power transistor.

Mainly breakdown region, cutoff region, active region, and saturation region are the regions.

Power transistor as a switch

Power transistor as a switch
Power transistor as a switch

When the power transistor works as a switch, the working is done between saturation and cutoff region, the ON and OFF switching operation is done between these operation regions.

Power transistor as an amplifier

Power transistor as an amplifier
Power transistor as an amplifier

When a transistor works as an amplifier, the transistor will work on active or linear

In the region, at active or saturation, the maximum capability of the transistor will be utilized.

Applications of power transistor

  • Switched-mode power supply (SMPS)
  • Relays
  • Converters
  • Power amplifier
  • DC to AC converters
  • Power supply systems
  • Power control circuits
  • Inverters
  • Voltage regulator circuits
  • Used for integrated circuits
  • Used at touch switch applications
  • Used at communications such as radar, etc.

Explain the main applications of the Power transistor

  1. Switched-mode power supply (SMPS)

The main application based on power transistor is the switching, the switched-mode power supply (SMPS) are been works with a combination of multiple switching sections.

  1. Power amplifier

The power transistors had an important role play in power amplifier circuits, normally amplifiers dissipate a higher amount of heat, this is because they can handle a higher amount of power.

Power transistor list

Transistor listTypeCollector-EmitterCollector CurrentDC Current GainPower Dissipation
Voltage (VCE)(IC)(hFE)(PD)
2N3055NPN60V14A20 to 70155W
2N6036PNP, Darlington-80V-4A750 to 1500040W
2N6039NPN, Darlington80V4A750 to 1500040W
2N6109PNP-50V-7A30 to 15040W
BD139NPN80V1.5A40 to 25012.5W
BD140PNP-80V-1.5A40 to 25012.5W
MJE2955PNP-60V-10A20 to 7075W
MJE3055NPN60V10A20 to 7075W
MJE13007NPN400V8A8 to 4080W
TIP31CNPN100V3A10 to 5040W
TIP32CPNP-100V-3A10 to 5040W
TIP35CNPN100V25A15 to 75125W
TIP36CPNP-100V-25A15 to 75125W
TIP41CNPN100V6A15 to 7565W
TIP42CPNP-100V-6A15 to 7565W
TIP48NPN300V1A30 to 15040W
TIP50PNP-400V-1A30 to 15040W

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