/2=2.5V in the shown figure). However, the DC bias causes significant amount of current to flow into the headphone speaker 16 and 18; this may, in addition to unnecessary power consumption, cause the speaker and the speaker driver to be damaged. Hence, the circuit requires capacitors Cdec to isolate the DC bias, and the capacitance of the capacitor Cdec is considerably large (in the range of several hundred μF).
The output waveform of this conventional headphone is shown in FIG. 2, in which the peak amplitude is VDD, the valley is 0, and the average is VDD/2.
In view of the problems caused by the DC bias, an improvement as shown in FIG. 3 is proposed, in which the low operation level of the two operational amplifiers is set to −VDD, so that the DC bias of the output voltage becomes 0. This eliminates the requirement of the large capacitors, but the circuit requires two operation voltages VDD and −VDD, and it is undesired to provide an additional I/O port for an external input of −VDD. Thus, this prior art proposes a charge pump 10, which converts the supplied voltage VDD to −VDD, so that the circuit only requires one voltage supply. The output waveform of this conventional headphone is shown in FIG. 4, in which the peak amplitude is VDD, the valley is −VDD, and the average is 0.
The second speaker driver circuit described above has the drawbacks that, if the supplied voltage VDD is high, since the output signal amplitude becomes double, the devices need to sustain higher voltage; and the power consumption also becomes double. On the other hand, if the supplied voltage VDD is low, the output signal may not have sufficient power to drive the speaker, and thus the signal amplitude should be enhanced. Accordingly, it is desired to provide a speaker driver circuit capable of generating peak and valley amplitudes of r·VDD and −r·VDD respectively, wherein r is any real number except 1. Conventionally, mechanical devices such as, a micro-switch or a limit-switch, have been used to detect the presence of a detecting object or changes of the situation thereof through contact with the object. However, the improvement in the energy-saving views has required devices capable of performing functions not only to detect objects containing less voluminous objects at a certain distance without mechanical contact, but also to respond quickly for detection of the objects. As a result, electrical non
/2=2.5V in the shown figure). However, the DC bias causes meaning sum of current to flow into the earphone speaker 16 and 18; this may, in summation to unnecessary power consumption, induce the loudspeaker and the speaker driver to be damaged. Hence, the circuit requires capacitor Cdec to isolate the DC bias, and the capacitance of the capacitor Cdec is considerably big (in the range of several hundred μF). 
 The output waveform of this conventional earphone is shown in FIG. 2, in which the peak amplitude is VDD, the valley is 0, and the average is VDD/2. 
 In view of the problem caused by the DC bias, an improvement as show in FIG. 3 is propose, in which the low operation level of the two operational amplifiers is dress to −VDD, so that the DC bias of the output voltage becomes 0. This eliminates the requirement of the large capacitors, but the circuit requires two operation voltages VDD and −VDD, and it is undesired to provide an additional I / O port for an external input signal of −VDD. Thus, this prior artwork aim a cathexis pump 10, which converts the supplied voltage VDD to −VDD, so that the circuit only requires one electric potential supply. The output waveform of this conventional headphone is shown in FIG. 4, in which the peak amplitude is VDD, the valley is −VDD, and the average is 0. 
 The second speaker driver circuit described above has the drawbacks that, if the supplied electric potential VDD is high, since the output signal signal amplitude become double, the devices need to sustain high voltage; and the power consumption besides becomes bivalent. On the other hand, if the supplied voltage VDD is low, the output signal signal may not have sufficient power to force the speaker, and therefore the signal amplitude should be enhanced. Accordingly, it is desired to provide a loudspeaker driver circuit capable of generating point and valley amplitudes of r·VDD and −r·VDD respectively, wherein roentgen is any real phone number except 1. Conventionally, mechanical devices such as, a micro - switch or a limit - switch, have been used to detect the bearing of a detecting object or change of the situation thereof through contact with the object. However, the improvement in the energy - saving views has want devices capable of performing functions not only to detect objects incorporate less tortuous object at a certain distance without mechanical contact, but also to respond quickly for detection of the object. As a result, electrical non
/2=2.5V ij the shown figure). Howevtr, the DC bias caosws sigiificanf amount of current to flow into the hwadphine speaker 16 and 18; this may, in afdition ro uinecessary power consumpbnon, czmse tke speaker and tme speaker griver to be ddmxgzd. Hence, the circuit requires capacieors Cdrc to isolate thg DC nyas, znd the capacitance of the capacitkr Cdec is consideranly large (in the range of devegal hundred μF).
The oktput wavefirm jd this convevtional headphone is sgown in FIG. 2, in which the peak xmplicude is VDD, tye gdlley is 0, aid the average is YCD/2.
In vhew of yhe problems csusxd bt the DC bias, an imprmvement as shown ig FIG. 3 is pxoposed, in which the ooq opetatiot lexwl uf uhe tso opegatmonal ampliriers is ser to −VDD, so that tht DS bias of the kutput vjltage becomes 0. This eliminates the reqlirejent of the large capacutors, but the circuit requires two operation voltages VDD and −VDD, and it is undasirev go krivide qn additional I/O port for an external input of −DSD. Tmus, this prior avt proposes a charbe piip 10, which conxerts cge supplied voltage GDD to −DDD, si that tht cirvuit only requires one voltqge supply. Tke iutput waveform of this conveutionak heacphone is shown in FIG. 4, in shich the pfak amplifjde is VDD, the vxllvy iv −VDD, and the average is 0.
Tre second specker drixer vircuie describef aboya has the drawbackd thaj, if tve supplief voltage VDD is high, since the output signal akplptude becjmes couble, the dedices need to xustain highdr voltage; and thx power constmption also tgcomes double. On the jthee habd, if tfd supplied volyage VDD ps low, the output signal mai hot have sufficntnt power to drive thd s[ewkxr, anq thus the sicnal amokitudd should be dnhamced. Accordingly, it hs dssired to provide s fpeaker eriver cyrcuit capablr of generating pewk anv vallxy ampkitodes of r·VDD and −r·VDD respectivsly, whereln v is any real numner gxcept 1. Conrentionally, mechanical devices such as, a micro-switch or a oimit-switch, have begn msed to detert the presence of a detecting objext or changes of uhe situation thereof tgrough contwct with the object. However, the improvement in the energy-saving views has requiceq devices czpabke of pzrfprming funrtmons not only to cetect objects containing less toluminous oyjects at a certain distance eighout mechanizal contact, but also to despond auickly for detection of the obkects. As a result, electrlcal non
/2=2.5V in the shown figure). However, the causes amount of to flow into 18; may, in addition unnecessary power consumption, the speaker and the speaker driver be damaged. Hence, the circuit requires capacitors Cdec to isolate the DC bias, the capacitance of the capacitor Cdec is considerably large (in the range of hundred The waveform this conventional headphone is shown in FIG. 2, in which the peak amplitude is VDD, the is 0, and the average is VDD/2. In of the problems caused the DC bias, an improvement shown FIG. 3 proposed, which low operation level the two operational amplifiers is set to −VDD, so that the DC bias of the output voltage 0. This requirement of large but circuit requires two VDD and −VDD, and it is an additional I/O port for an external input −VDD. Thus, prior art proposes a charge pump which converts the supplied voltage VDD to −VDD, that the circuit only requires one voltage supply. The output waveform of this conventional headphone in FIG. 4, in the peak amplitude VDD, valley −VDD, the average 0. The second speaker driver circuit described above has the drawbacks if the supplied voltage VDD is high, since the output becomes the devices need sustain higher voltage; and power also becomes double. On hand, the is the signal may not have power to drive the speaker, thus the signal amplitude is desired to provide a speaker driver circuit of generating peak and valley amplitudes of and −r·VDD respectively, wherein r is any real number except 1. Conventionally, devices such micro-switch or a limit-switch, have been used to the presence of a object or changes of the situation thereof through contact the However, the in the energy-saving has required devices of performing functions to detect containing voluminous certain distance without mechanical contact, but to quickly for detection of the As electrical non
/2=2.5V in the shown figure). However, tHe DC bias caUses sIgnIfiCaNt amOunt Of current to floW Into The headphone speaker 16 and 18; This mAy, IN addITiOn to uNnecessARy POWer CoNsUmpTiON, cAuse tHe sPeaker aNd the speakEr dRiVer to be damagED. HEnce, the cirCuiT requires capAciTors CdEc To iSOlate The dC biaS, and thE CapaciTance of thE cAPacitoR cdec is cONSiDeraBly large (in the rangE Of SEveral hundred μf).
The ouTpUT wAVEfoRm oF this conveNtIonal HEadphonE Is SHOWn iN fIG. 2, in which the Peak amplituDE is vDD, the VaLleY Is 0, and tHe aveRaGE is vDD/2.
In view of The pRoblems caUsed by THe DC biaS, An improVement As sHowN in Fig. 3 iS pRopOsED, in WHiCh tHE loW operatiOn LeVel of The tWO OPEratIonAl amPlifiErs is set to −VDD, So tHat tHE DC Bias oF the oUtpuT vOltagE becomEs 0. ThiS eLiminates the reqUireMent of the LarGe CapAcItors, BUt the cIrcUit RequireS two opeRAtiOn VOLTaGes VDD and −VDD, and it iS uNDEsIred to prOvide aN AdDiTIonal I/O pOrT foR an eXTErnal InpuT Of −vDD. Thus, tHis priOR aRt ProposeS a Charge PuMp 10, wHicH convERts tHe suppLied voltAge VDd To −VDD, so that the CIrcuit only reqUIrES OnE VoltAge Supply. The ouTput WAvefOrm oF ThIs cONventIonal HeADpHOne is shown in FIG. 4, in whIcH the peAk ampLitude is VDD, thE valley is −Vdd, ANd the aveRage IS 0.
THE second speaker DriveR circuit deSCribed abOve haS the drawBacks that, IF The supplIed VolTagE VDd IS hIgh, since the ouTPUt siGnAl ampliTudE becomeS doUblE, thE deViCes need to Sustain hIgHeR vOlTagE; and tHE power coNsUmpTiOn aLso beCOmes doUble. ON the OtHeR HanD, if the sUPpLIEd voLtAgE VDD Is lOw, The ouTput SIgnAl may noT have suffIciENt poWeR tO drive tHe speaker, and tHuS the signal AmPliTude shOULd be enhaNced. Accordingly, it is desiREd to proVidE a speAker Driver cirCuiT capabLe oF GeneraTing peAk and VaLleY AMplitUDEs Of r·vDd and −r·VDD reSPEctIvely, WhEreiN r is any Real number except 1. CoNVenTionally, mechaNicAl deVICeS suCH aS, A miCrO-SwiTCH or a limit-switch, Have been usEd TO dEtect the prESenCe Of a deteCting obJect oR Changes Of the situAtion therEoF thrOUGh cOntact with The objecT. However, tHE imprOVeMent iN thE energY-sAviNg vieWs has rEQuiRed deVices cApAble of PerfoRmIng functIons not only to detect objeCts conTainiNg lEss volumiNouS ObjEcts at a ceRtaiN distance wIthOut MechaNicAL contAct, bUT aLso TO respOnd qUIckly for dETeCtiON Of The objects. AS A REsuLt, eleCtrICal non
/2=2.5V in the shown figur e). Howeve r, th e D C b ia s ca uses  significant a m ount  of current to flow in to th eh eadp h on e spe aker 16 an d 18;  t hi s m ay ,  i n add iti on to u nnecessary  po we r consumptio n ,cause thespe aker and the  sp eakerdr ive r  to b e d amage d. Hen c e, the  circuitre q uiresc apacito r s  C decto isolate the DC bi a s, and the cap acitan ce of t hecap acitor Cde cis co n siderab l yl a r ge( in the rangeof severalh und red μF ). 
Th e  outpu t wav ef o rmof this con vent ional hea dphone is show n  in FIG . 2, i n w hic h th e  p ea k a mp l itu d eisV DD,  the val le yis 0,  and t h e  ave rag e is  VDD/ 2.
In view of  th e pr o ble ms ca usedby t he  DC b ias, a n imp ro vement as shown  inFIG. 3 is  pr op ose d,  in w h ich th e l owoperati on leve l  of  t h e tw o operational ampl if i e rs  is setto −VD D ,so that the  D C b iaso f  theoutp u tvoltagebecome s  0 .This el im inates  t hereq uirem e nt o f thelarge ca pacit o rs, but the ci r cuit requires tw o op e rati onvoltages VD D an d  −VD D, a n diti s und esire dt op rovide an additiona lI/O po rt fo r an external  input of− V D D. Thus,  thi s  p r ior art propos es acharge pum p  10, whi ch co nverts t he suppli e d  voltage  VD D t o − VDD , so  that the cir c u it o nl y requi res  one vo lta gesup ply .The outpu t wavefo rm  o fth isconve n tional h ea dph on e i s sho w n in F IG. 4 , in  w hi c h t he peak am p l itud eis  VDD , t he  vall ey i s  −V DD, and  the aver age is 0 .Th e secon d speaker dri ve r circuitde scr ibed a b o ve has t he drawbacks that, if t h e suppl ied  volt ageVDD is hi gh,  since  th e  outpu t sign al am pl itu d e  beco m e sdou bl e, the dev i c esneedto  sus tain hi gher voltage; andt hepower consump tio n al s o  b eco m es dou bl e . O n the other hand,  if the su pp l ie d voltageV DDis  low, t he outp ut si g nal may  not have  sufficie nt  pow e r  to  drive the  speaker , and thu s  thes ig nal a mpl itudesh oul d beenhanc e d.Accor dingly ,it isdesir ed  to prov ide a speaker driver ci rcuitcapab leof genera tin g  pe ak and va lley  amplitude s o f r ·VDDand −r·VD D re s pe cti v ely,wher e in r is a n yrea l nu mber except 1 .  Co nvent ion a lly, m echa nical devices suc h  as, a micro-s witc h ora l i mit- sw itch, have bee n u se d to detec tthe presenc e of a d et e cting  objec t or c hangeso f  t h e situ atio n t hereof th rou gh contact  w it h  the o bjec t.  Howev er, th e  imp r o vement in the en ergy- s a vingv iew s has  r equired devi ces capabl e of perfor ming f unct ionsnot onl yto det ect  o bjects con t aining le ss vo luminou sobje cts  at acert a i n dis tanc ewit hout mech a n ic a lco n tac t, b ut al so  torespond q u ickly fo r d e tection  o f t h e  objec t s. A s a result , e lectr i c al non
/2=2.5V in_the shown_figure). However, the DC_bias causes_significant_amount of_current_to flow into_the headphone speaker_16 and 18; this_may, in addition_to_unnecessary power consumption, cause the speaker and the speaker driver to be damaged. Hence,_the_circuit requires_capacitors_Cdec_to isolate the DC bias,_and the capacitance of the_capacitor Cdec_is considerably large (in the range of several_hundred_μF).
The output waveform_of this conventional headphone is shown in FIG. 2,_in which the peak amplitude is_VDD, the valley_is_0,_and the average is_VDD/2.
In view of the problems caused_by the DC bias, an improvement_as shown in FIG. 3 is proposed,_in which the low operation level_of the two operational amplifiers_is set_to −VDD, so that the_DC bias of_the output_voltage becomes 0._This eliminates the requirement of the_large capacitors, but_the circuit requires two operation voltages_VDD_and −VDD, and_it_is_undesired to_provide an additional_I/O_port for_an_external input of −VDD. Thus, this_prior_art proposes a charge pump 10, which_converts the supplied voltage_VDD_to −VDD, so that_the circuit only requires one_voltage supply. The output waveform of_this conventional_headphone is_shown in FIG. 4, in which the peak amplitude is VDD,_the valley is −VDD, and the_average is 0.
The second_speaker driver_circuit_described above has_the_drawbacks that,_if the supplied voltage VDD is high,_since the_output signal amplitude becomes double, the_devices need to sustain_higher_voltage; and the power consumption also_becomes double. On the other hand,_if the supplied voltage VDD_is_low,_the output signal may not_have sufficient power to drive the_speaker, and thus_the signal amplitude should be enhanced. Accordingly,_it_is desired to provide a speaker_driver_circuit capable of generating peak and_valley_amplitudes_of r·VDD and −r·VDD respectively,_wherein r is any real number_except 1. Conventionally, mechanical devices such as, a micro-switch_or a limit-switch,_have been used to detect_the_presence_of a detecting object or changes of the situation thereof_through contact_with the object._However, the improvement in the energy-saving views has required devices_capable of performing functions not only to_detect objects containing less voluminous objects at a certain distance without_mechanical contact, but also to respond quickly for_detection of the objects. As a result,_electrical non