TIP122 is an NPN Darlington transistor, darlington transistor means there are two transistor in one package connected to increase gain at output. TIP122 transistor has a lot of good features like 5A collector current, max emitter-base voltage is 5V, max collector dissipation is 65 watt, minimum & maximum current gain is equal to 1000. This transistor is designed to use as a switch and for amplification purposes.
How to Safely Long Run in a Circuit:
To get better performance with this Darlington transistor we suggest to always staying below its maximum ratings. Do not operate it in circuits using more than 100V. Do not provide load more than 5A. Always use a suitable base resistor to provide required current at its base. Use a suitable heatsink to save it from overheating and do store or use it in temperature below -65 centigrade and above +150 centigrade.