How easy is it to destroy a SN754410. I've connected one with 5V on pin 1 & 16, 12V on 8 and grounded pins 4, 5, 12 & 13. With this setup with no input on 2, 7, 10 & 15 there should be no output at all but I measure 11.8V on pins 3, 6, 11 & 14. That leads me to believe I've somehow destroyed the IC. I've tried with 2 other ICs and they react the same way. Have I overlooked something?