A Darlington pair NPN transistor is the TIP122. It performs the same functions as a standard NPN transistor, but because it contains a Darlington pair, it has a good 5A collector current rating and a gain of roughly 1000. It can drive high loads because it can handle roughly 100V across its collector-emitter. The internal circuit diagram of this transistor, which displays the Darlington pair inside of it, is shown below.
As you can see, this TO-220 package has two transistors, with the emitter of the first transistor connected to the base of the second and the collector of both transistors coupled to form a Darlington pair. This raises the transistor’s current gain and current rating.
A highly well-liked Darlington NPN transistor is the TIP122, which has a high current gain and high current. The term “Darlington” refers to a situation in which two transistors are available in a single pack to increase the gain at the o/p. This transistor can be produced for switch-like and amplification-related uses.
How to use TIP122?
Despite having a high collector current and current gain, TIP only has a low emitter-base voltage (VBE) of 5V and a base current of 120mA, making it relatively easy to manage. I used the TIP122 to control a 48V motor with a continuous current of approximately 3A in the circuit shown below.
Our load only uses 3A of the transistor’s 5A continuous collector current, which is acceptable. The highest base current is around 120mA, but I’ve reduced it to 42mA by using a high-value 100-ohm resistor. If your requirement for collector current is minimal, you can even use a 1K resistor.
Make sure your motor doesn’t use more than 8A of the peak (pulse) current of this transistor. This is only a model circuit diagram that illustrates how this transistor operates; it cannot be utilized in actual operation. You can therefore similarly manage your load.
A TIP122 transistor has the following pin arrangement. This transistor has three pins; the purpose of each pin is covered below.
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
Applications of TIP122 Transistor
Based on its characteristics, this transistor can be utilized as a switch in many electronic circuits to drive various loads below 5A. This transistor is mostly used in circuits for power supplies, motor drives, and battery chargers.
This transistor also functions as an audio pre-amplifier and amplifier. 5V DC is the transistor EB voltage. To regulate loads that draw less than 5A, this transistor can be linked to the microcontroller’s o/p & logic devices.
This transistor is employed anywhere strong amplification is required as well as for managing high current loads. A microcontroller, often known as a logic device, is used to control this transistor simply, but care must be taken to ensure that it can handle 120mA.
A logic device may simply control this transistor to switch maximum power loads or to magnify the maximum current. Therefore, this transistor is the ideal option for your needs.
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