What is TIP122 Transistor : Pin Configuration & Its Applications

The Darlington NPN transistor-like TIP122 includes Darlington braces & it works like a normal transistor however includes a Darlington pair. This transistor includes a decent collector current like 5A & the gain is approximately 1000. This kind of transistor bears 100 volts in the region of both the emitter & collector terminals because it can be utilized mainly for high loads.

What is TIP122 Transistor?

The TIP122 is a Darlington NPN transistor and it is very popular for its high current gain & high current. As the name suggests, the term Darlington means when the two transistors are available in a single pack for enhancing the gain at the o/p. The manufacturing of this transistor can be done like a switch & amplification purposes.

TIP122 Transistor
TIP122 Transistor

Pin Configuration

The pin configuration of a TIP122 Transistor includes the following. This transistor includes three pins where each pin and its function are discussed below.

TIP122 Pin Configuration & Symbol
TIP122 Pin Configuration & Symbol
  • Pin1 (Base): This pin controls the transistor biasing.
  • Pin2 (Collector): The flow of current will be there throughout this pin
  • Pin3 (Emitter): This pin is used to drain the current

Features & Specifications

The features & specifications of a TIP122 transistor include the following.

  • This transistor is available in the TO-220 package
  • This is an NPN Darlington type transistor
  • Max Operating & Storage Temperature Ranges from -65 to +150 C
  • Collector Current Max is 5A
  • DC Current Gain (Max & Min) is1000
  • Collector-Emitter Voltage Max is 100V
  • Collector Dissipation Max is 65 Watt
  • Collector-Base Voltage is 100V
  • Max Emitter-Base Voltage is 5V
  • Single configuration
  • Quantity in a pack from the factory is 200
  • Height is 9.4 mm
  • Length is 10.67 mm
  • ON Semiconductor Manufacturer
  • Mounting type & style is through-hole
  • The width is 4.83 mm

The TIP127 transistor is the complement transistor of the TIP122. NPN transistors from the same family are TIP121, TIP120, TIP122 whereas PNP Family transistors are TIP126, TIP125 & TIP127.

Where to use TIP122 Transistor/Applications?

This transistor can be used as a switch within different electronic circuits to drive different loads below 5A based on its features. The application circuits of this transistor mainly include a battery charger, power supply, motors driving, etc.


This transistor can also be used as an amplifier & audio pre-amplifier. This transistor EB voltage is 5V DC. This transistor can be connected to the microcontroller’s o/p & logic devices for controlling below 5A loads.

This transistor is used for controlling high current loads & also used wherever high amplification is necessary This transistor is simply controlled through a microcontroller which is called a logic device but care must be taken to verify if the microcontroller can capable of 120mA.

This transistor can be controlled easily through a logic device for switching maximum power loads for amplifying max current. So this transistor is a perfect choice for your requirement.

How to Protect a TIP122 Transistor in a Circuit?

To get good performance through this Darlington transistor, maximum ratings must maintain to below. This transistor shouldn’t use when the circuit is operated above 100V and the load shouldn’t provide above 5A. A base resistor must use for providing the required current on the base terminal.
From the overheating, this transistor can be protected by using a heatsink. Maintain the temperature from 65C to +150 C.

How to use a TIP122 Transistor?

The circuit diagram of a 100W powerful audio amplifier circuit is shown below. This circuit uses a TIP122 Transistor.

Audio Amplifier Circuit using TIP122
Audio Amplifier Circuit using TIP122

A simple audio amplifier circuit uses a weak audio signal & converts it into a powerful, better & clear audio signal. At present, these amplifiers are available in every consumer electronic device like camcorders, music players, smartphones, PCs & laptops. Here, we are designing a simple 100W audio amplifier circuit through the TIP122 transistor.

Darlington pair transistor like TIP122, audio jack-3.5mm/male, female-1, smart phone, terminal block connectors-2, loudspeaker-8 Ohm-1, 10K potentiometer-1, 470uF capacitor-1, 150K resistor-1, jumper wires & DC battery with clip.

The working of this circuit is as follows. This circuit is unique due to its high-power Darlington transistor and robustness. An audio transducer like a mic provides audio input that performs like the DC control signal used for the Q1 transistor.

Here, a 470uF capacitor works like a coupling capacitor and the main function of this is to block the signals of DC components & allows simply the AC component signals to supply throughout the circuit. Here, the ‘Q1’Transistor changes the signal and transmits it to the ‘Q2’ transistor’s base terminal.

Further, this TIP127 transistor changes the input signal and transmits it to a loudspeaker. Here loudspeaker is an audio output device. In the circuit, a 10K preset pot can be used to regulate the strength of the o/p audio signal.

Advantages & Disadvantages

The advantages of the Darlington pair transistor include the following.

  • It provides extremely high current gain as compared to a single transistor.
  • As compared to phototransistor including exterior amplifier, this transducers provides less noise
  • The input impedance provided by this transistor is extremely high
  • By using a current source with few mA, the designer can drive more power-based applications
  • It uses fewer components to make the circuit.
  • It is extremely responsive to current.
  • Signal amplification can be done for a long time

The disadvantages of the Darlington pair transistor include the following

  • Once this transistor is within the saturation region, there is a voltage drop beyond BE terminals.
  • The first transistor’s leakage current can be amplified through the second transistor. So, the Darlington transistor’s overall outflow current is higher.
  • Less switching speed
  • It provides max power dissipation because of high saturation voltage.
  • Limited BW (Bandwidth)
  • At certain frequencies, the phase shift can be introduced by this design within a negative feedback circuit.


The applications of the TIP122 Transistor include the following.

  • This transistor is used to adjust high current based loads like 5 amperes
  • It is used as a Power switch.
  • It is used where high strengthening is desirable.
  • It is used as a velocity controller within motors
  • It is used in rectifier circuits and inverters
  • It is used in smartphones, MP3 players, etc.
  • It is used in auditory weapons.
  • It is applicable in live music concerts, production & recording.
  • Used in different electronic circuits like rectifier, amplification, switching circuit with less power, inverter circuit & motor speed control.

Thus, this is all about an overview of a TIP122 transistor datasheet including high voltage & current. This kind of transistor is mainly used in normal amplification & a switching circuit with less speed. This transistor includes a Darlington pair, so its CC rating (collector current) is 5A & gain is 1000V. This transistor includes a 5V BE voltage & that can be controlled directly through a logic level device like a microcontroller. Here is a question for you, what is the function of a TIP122 Transistor?