Over the past couple of weeks, I've randomly noticed on several
occasions that some of my various ICs (MOSFET gate drivers, 74HC595,
opamps) are getting very hot to the touch.

I'm prototyping on a breadboard, and the power supply is a ~5V NiMH
battery pack. For all ICs, I'm using a linear regulator and several
decoupling capacitors around the regulator and the IC power supply pins,
and making sure that all inputs and outputs stay within the rated
voltage range.

It *seems* that some of them are sometimes getting hot enough to emit a
very slight burning smell, which I then confirm by touching the IC to
check its temperature. There doesn't seem to be a pattern as to when
they're getting hot. Disconnecting and reconnecting the battery pack
seems to (at least temporarily) fix the problem.

No switching regulators or inductors are involved. No PIC micro ever
seems to get hot like these random ICs do. All IC high-Z inputs are
connected to GND, and all IC low-Z outputs are either left floating or
connected to a high-Z input elsewhere.

Any ideas as to what could be causing this?
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