TIP31C NPN Transistor : Pin Configuration & Its Applications

The TIP31C NPN transistor is available in the TO-220 plastic package and it is used frequently in a wide range of applications like audio, switching, power linear, etc. The PNP type transistor is TIP32C. This is a bipolar junction transistor including three terminals like emitter, base & collector.


The base terminal is lightly doped whereas the other two terminals like collector & emitter are highly doped. This TIP31 transistor is very cheap and quite simple to use in several applications. This article discusses an o overview of TIP31C NPN power transistor, pin configuration, circuit, working, and its applications.

What is TIP31C NPN Transistor?

TIP31C is an NPN transistor that is available in the TO-220 package. The main purpose of this transistor is to use in general purpose applications. These types of transistors are available in four different types but they vary based on the series used after the number of transistors like TIP31A, TIP31, TIP31C & TIP31B. These series of transistors have different voltage ratings.

TIP31C NPN Transistor Pin Configuration
TIP31C NPN Transistor Pin Configuration

As compared to other series of transistors, the TIP31C series transistor will have a maximum load voltage like 100V but the collector current is similar to 3A. This transistor is used for amplification & general purpose applications.

Once this transistor is used as a switch then it is capable of quick switching & drives different loads at a time. It can also be used in audio amplifier stages.

Pin Configuration

The pin configuration of the TIP31C NPN transistor is shown below. This transistor includes three pins where each pin and its functionality are discussed below.

  • Pin1 (Base): This pin is used like TRIGGER for activating the transistor.
  • Pin2 (Collector): This pin is connected to load
  • Pin3 (Emitter): This pin is connected to the GND terminal

Equivalent TIP31C transistors are 2N6122, TIP31A, MJE340K, TIP31B, and SW4F013. But we need to verify different parameters of this transistor before changing carefully like current, voltage & gain which may cause permanent injure. Similar TIP31C transistors are TIP121, TIP120, TIP122, 2N6290, 2N6288 & 2N6292

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Specifications & Features

The specification and features of the TIP31C NPN transistor include the following.

  • It is available in TO-220 Package
  • Operating temperature ranges from -65 to +150 C
  • NPN type Transistor
  • DC gain max & min 10 – 50
  • Collector current Max is 3A
  • Transition frequency max is 3 MHz
  • Collector to emitter voltage max is 100V
  • Dissipation of collector current max is 40 Watt
  • Collector to base voltage max is 100V
  • Emitter to base voltage max is 5V
  • Saturation voltage is low
  • Easy drive supplies
  • The operating area is very safe
  • For less distortion paired designs
  • Simple handle & carry

How to use TIP31C NPN Transistor Very Safely?

This transistor is used very safely to run for many years. For that, we need to stay 20% under the highest ratings. Because maximum rating of components may reduce the life span so an appropriate base resistor is used to provide the necessary base current toward the transistor.

Do not drive load above 3A & 100V, do not drive above 5A load in pulse/ peak mode. Temperature of this transistor should be from > -65 C < +150 C.


Darlington TIP31C NPN Transistor to Drive DC Motor

Generally, a potentiometer cannot control DC motor speed directly because they draw huge amounts of the current so there is more chance to burn the potentiometer. As an alternative, a potentiometer with a small amount of current can be changed to run the DC motor with Darlington Pair of TIP31C NPN transistor.

So the circuit using Darlington transistors to drive the DC motor is shown below. This circuit can be built with a potentiometer, Darlington transistor (TIP31C NPN Transistor), 1N4148 diode & DC motor. In the above circuit, a linear potentiometer is allied in between Vs & 0V.

Darlington Transistor to Drive DC Motor
Darlington Transistor to Drive DC Motor

So that the voltage at the wiper terminal in the potentiometer will always be anywhere otherwise they stay in between the two circuit voltages. Once the small amount of current flows throughout the wiper within the potentiometer, then the voltage will be immediately changed by a Darlington pair transistor.
The flow of current from the variable resistor can be changed throughout the two transistors by increasing the flow of current greatly & which can be controlled through the variable resistor.

The main drawback of this circuit is, the Darlington transistor is not completely linear so the modification within the speed of the DC motor for a specified rotation of the variable resistor will more delicate in the center of its range. Since a DC motor is an inductive load, it will generate a ‘back-emf which may damage the second transistor. A diode like 1N4148 will prevent this harm by shorting out this back emf.

The power supply of this circuit can be provided from the rectifier directly. This rectifier will help in preventing the sticking motor ‘at less speed. The maximum voltage supply provided is 60V & the highest motor current utilization is 3A.

Where to use/Applications

The applications of the TIP31C transistor include the following.

Once you need a simple switching device to use in loads that use medium power, then the TIP31C transistor is very useful. These transistors are available very easily with less cost.

When you need to amplify a signal, then the transistor amplifying factor is quite good & the gain is nearly linear. Consequently, these characteristics will make this transistor one of the finest components use in amplifying applications.

This kind of transistor is used to control the microcontroller signals due to its quick response and gain. Thus it can be simply used in high-speed-based switching applications.

  • Used to control the speed of DC motor
  • Signal & audio amplifiers
  • Lighting systems
  • PWM applications
  • Relay drivers
  • SMPS or Switch mode power supply
  • Darlington Pair
  • Designing power supply circuits
  • Audio amplifiers
  • Switching loads below 3000mA/3A
  • Stages of audio amplifier
  • Motor driver-based applications
  • Designing of circuits for battery chargers

Thus, this is all about an overview of the TIP31C NPN transistor datasheet which includes pin configuration, specifications, features, circuit, and its applications. This is a bipolar power transistor, mainly is designed to use in switching & general purpose amplifier applications. Here is a question for you, what is an alternate transistor to TIP31C?

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