Patent ID: 7696808

Claim:
A slew rate controlled output driver for a lower power transistor coupled between a power ground terminal and an output terminal in an audio power amplifier, comprising: a P-type MOSFET that is connected to a power source and a gate of the lower power transistor and turns on the power transistor by charging up a gate capacitance of the power transistor; a first N-type MOSFET, coupled between the gate of the lower power transistor and the power ground terminal, that provides an uninterrupted discharging path for the gate capacitance of the power transistor; a second N-type MOSFET that is adequate to turn off the power transistor by discharging the gate capacitance; a first switch between the gate of the lower power transistor and the second N-type MOSFET, wherein turning-off of the first switch reduces a discharging speed of the gate capacitance from a path of the second N-type MOSFET; a second switch between the gate of the lower power transistor and the second N-type MOSFET, wherein turning-off of the second switch further reduces the discharging speed of the gate capacitance from the path of the second N-type MOSFET; an output level detector, coupled to the output terminal, that controls the first switch, and is activated when an output level of the output driver rises above a predetermined value; and a power ground (PGND) level detector, coupled to the power ground terminal, that controls the second switch, and is activated when a power ground level drops below another predetermined value.