Dave Smith
but if you have the AT controlling the approach speed what happens if you command more thrust?
The way Boeing A/T works, throttle position always equates to thrust command. There are friction 'brakes' the connect the throttle levers to the autothrottle drive - if you don't like what the A/T is doing or want to override for any reason, it takes ~2.5 lbs. force at the knob to make the brake slip and move the throttle independent of the A/T (i.e. ~5 lbs. total for a twin or ~10 lbs. for a 747-400/-8).
Now, once you override the A/T, unless you disconnect the A/T (button on the thrust lever) the A/T will continue to try to drive the throttle so you'd need to continue holding the thrust lever.
This is pretty much common across the Puget Sound built Boeing aircraft.
Clear enough?