Abstract: An improved class D power amplifier is disclosed. Instead of using prior art triangle waves, a ramp signal having a first state of about 90% or greater is used and a second state for the remainder of the cycle. Further, the amplifier includes flip-flops and amplifers with hysteresis to reduce switching noise. Also, level shifting circuitry is provided for shifting the level of the input signal in response to both DC and AC variations in the power supply and to provide power supply rejection. Still further, multiple channels may be used with all of the channels synchronized to the same timing source.

Abstract: Two emitter follower transistors (260, 250), in which each transistor has an emitter coupled to one of the collectors of a differential pair structure (230, 240)to form two stacked transistor pairs (260, 230) and (250, 240). A first differential signal (IN, INX) is positive supply referenced (Vcc) and is coupled to the bases of the emitter follower transistors (250, 260). A second differential input signal (275, 295) is coupled to the bases of the differential pair transistors (230, 240). The second differential input signal (275, 295) is identical to the first input signal but also includes a voltage level shift from the positive supply (Vcc). The first and second input signal portions are coupled to the transistors which make up the stacked transistor pair (260, 230) and (250, 240) and are chosen so that they are 180 degrees out of phase.