Not a particular circuit. Just learning. But i did build up a circuit the other day in the sim that matches what was described above.
However i have found something that didnt match

Say i have a comparator sinking current right to ground.
According to the sim, the power dissipated is strictly the supply voltage * the Q current.
The comparator is sinking about 3 mA to ground and its not showing up in the power calculation. Not sure why.....

 

Load current times saturation voltage for the LM339 output voltage and similar

 

The typical output saturation voltage of an LM339 comparator when its output current is 3mA is shown in its datasheet as 0.25V. Then the dissipation in the output transistor is 0.25V x 3mA= 0.75mW.

The dissipation in the output transistor of an opamp is usually much more because its output is usually linear and is rarely saturated.