When dealing with an Op Amp driving one or more 150 ohm loads, the Op Amp power dissipation can be calculated to make sure under worst case ambient temperature the device junction temperature is not violated. The worst case ambient limit imposed by the Op Amp is usually around 85 degrees C, and the junction temperature limit is in most cases 150 degrees C for most processes. Of course, to minimize failure rate and premature aging of the device, the junction temperature should be kept well below the 150 degrees C absolute maximum rating. The figure shown represents the simplified output waveform across a single 150 ohm load. The analog video waveform shown is the worst case pattern possible in terms of power dissipation. This is called a white field and will result in a pure white field on a color monitor if all three colors are simultaneously driven. The reason this is the worst case for power is that the video voltage is a simple DC voltage at maximum amplitude of 1.4 volts throughout the horizontal active time. The active time would be anywhere from .75 to .90 of the H period shown, or the horizontal period, which is the total horizontal time. On the right, you see the Op Amp push-pull output transistors Q1 and Q2 which alternatively drive the sourcing and sinking current into the 150 ohm load. Assuming DC coupling with the levels shown, the output stage must deliver sourcing current for most of the period because the only time the output sinks current is during the sync time, which is a very small fraction of the total period. Therefore, all load-related power dissipation in this case is in the top transistor, Q1. The power dissipated is calculated in the expression shown here. As you can see, the dissipation needs to consider the duty cycle of the active waveform, taken as 90% in this case worst case, or the .9. Keep in mind that the total device power would be the sum of the power dissipated in Q1, plus the device quiescent current. If you have multiple channels, of course, you need to consider all the channels also. This is a single one shown here. IS shown is the Op Amp supply current under no load. This can be anywhere from less than one milliamp up to more than 10 milliamps per Op Amp.