TIP122 is an NPN transistor that functions as the ordinary NPN transistors but has a better collector current of 5A and a gain of 1000 because of the presence of a Darlington pair in it. It is used to drive heavy loads because its collector-emitter can withstand up to 100V.
The package coming with TIP122 has two transistors. The first emitter’s transistor is connected with the base of the second one. To form a Darlington pair, the collector of the two transistors is connected. In addition to adding the current gain of the transistors, tying them together also increases their current rating.
The base-emitter in TIP122 has a low voltage of 5V and can only be controlled by logic devices like microcontrollers.
According to its datasheet, some of the main specs of the transistor are:
- Base Current of 120mA
- Emitter Base Voltage of 5V
- Collector-Emitter Voltage of 100V
- Collector Base Voltage of 100V
- Continuous Collector Current of 5A
- High DC Current Gain of 1000
- Darlington Medium Power NPN Transistor
The following are the key application areas for the transistor:
- Speed controlling motors
- Rectifier circuits and inverters
- Medium power switches
- Switching high current loads; of up to 5A
TIP122 pinout
TIP122 has three pins. Pin 1 is the base pin that controls how the transistor is biased, and it is used to turn the transistor on and off. The collector pin is the second one, and it is where current from the collector flows in through. Pin 3 is the emitter pin where the current drains out and is connected to the ground.
Have a look at the pinout diagram above.
TIP122 Equivalents and Replacement Details
TIP122 is a Medium Power NPN Darlington Transistor. Equivalents for TIP122 are KSD560, BDW2, BDT63, 2SD1415, and TIP127. The maximum base current of the TIP122 is 120mA, and the peak current of the transistor is 8A, therefore, when using it, you should ensure your motor does not require more than that.