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If you don't use any base resistor to limit the current you will have a huge base-emmiter current in the output transistors which can damage them
this is the result of driving TIP122 with a constant current source of 20mA (simulating a PIC output) , 9v power supply
View attachment 60856
Alex
Slightly off-topic, but since you are using this for an inverter, why don't you use MOSFETs? You will get much better efficiency, all you need is a good drive circuit. With a drive circuit employing 2 to 3 transistors, you can drive the MOSFETs with very little current. You could even use logic level MOSFETs. Plus, they have a positive thermal coefficient, so they can be better paralleled.
Hope this helps.
Tahmid.