3 and 4 the charge pump is part of the headphone amplifier 5 with a loudspeaker 6 providing just the amount of power that according to gain settings is required in normal operation the charge pump is driven according to the audio volume fig1 provides a schematic overview of the switches involved to realize the various operating modes in total 8 switches are employed some of the switches have an integrated bulk switch an example implementation with all nmos switches is shown in fig1 the switches with associated capacitor symbol have an integrated charge pump which provides the necessary gate source voltage for nmos transistors which are used as high side switches switches s 1 s 3 and s 5 are nmos switches with internal integrated charge pump signified in fig1 by a capacitor sign where an internal capacitor in each switch is charged to vdd voltage and then connected between source and gate of a power nmos switch to switch on in order to switch off the gate is shorted to source these switches are designed to operate only with terminal voltages between 0 to vdd fig4 illustrates a preferred embodiment of such an integrated charge pump 40 providing the necessary gate source voltage for transistor switch 41 representing switches s.