Hi Eugene!

I thought you were using a tiny buzzer... that's why I suggested that circuit. I guess Kai's schematic has brought some light to our problem...

As you have done the test proposed by Kai, and your MCU is incredibly still working after driving this thing with a 27 ohm resistor, this might solve your problem:

1) Buy a TIP125 (or TIP126, TIP127), it's a PNP Darlington transistor (this means you can get high currents in the collector, with a low current in the base). I am suggesting this because it should be cheap and easy to find, hFE = 1000, máx Icollector = 5A, and it has a protection diode for reverse voltage (so, it's hard to get fried).

2) Connect it the same way I suggested before (PNP transistor), but instead of a 10k resistor in the base, use a 330 ohm resistor (you can try smaller values, if necessary, but be careful to don't use a value smaller than 180 ohm).

Tell us the results.