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OPA549 Over Heating Problem

Other Parts Discussed in Thread: OPA549

I am designing a motor driver circuit for a product I am designing using the OPA549. Straight forward common design.

Problem is even at low currents (0.5 to 1 Amp) the OPA549 quickly heats up to thermal shutdown  (I have a heat sink on the chip).  The circuit configuration is a typical non-inverting op-amp configuration using 5.1k/13k (a gain of about 3)  resistors for feedback on the negative input. Power supply is from a 12 volt battery and is decoupled at the chip with the recommended 10uf and 0.1uf capacitors. Basically my circuit is nearly identical to the application notes recommendations. 

The output of the amplifier has a 0.25 ohm power resistor and I replaced the motor with a 1 ohm power resistor for test purposes. The input to the amplifier is from a DAC on a microprocessor. Ideally I will be driving the motor with a sine wave at about 6v p-p at <400hz and at about 4 amps rms.

With an ammeter on both the power input and the current through the output, at only 0.5 amps the op-amp heats up very fast, but I am only seeing the expected 0.5 amp of current at both points. I set the input at a dc voltage so the output is dc. Even with a sine wave drive the chip heats up. Looking at power, inputs, outputs,... with my oscilloscope I do not see any oscillations.

Seems to me that the chip should not get that hot at only a half amp of current.

I am stuck as to what else to check. Any suggestions?