Molecular ad Quatum Acoustics vol. 7, (6) 95 DGTALL TUNED SNUSODAL OSCLLATOR USNG MULTPLE- OUTPUT CURRENT OPERATONAL AMPLFER FOR APPLCATONS N HGH STABLE ACOUSTCAL GENERATORS Lesław TOPÓR-KAMŃSK Faculty of Electrical Egieerig, Silesia Uiversity of Techology, Krzywoustego Str, 44- Gliwice, POLAND, ltopor-kamiski@polsl.pl The coceptio of multiple output curret operatioal amplifier ad its applicatios i curret amplifiers circuits havig amplificatio digitally tued, has bee preseted. The geeral structure of the realisatio of a siusoidal geerator with oe MOCOA ad digitally tued parameter such as a coditio ad frequecy of oscillatio, has bee described. Oe versios of a siusoidal oscillator with RC elemets, have bee show. Simulatios the form of geerated oscillatios as amplifier output curret, have bee carried out ad the effect of tuig of its amplificatio o the form of those characteristics, has bee ivestigated. The system may be applied i high stable acoustical geerators. Keywords: curret operatioal amplifier, siusoidal oscillator, digitally tued circuits, multiple output amplifier. NTRODUCTON With the developmet of computig techiques as well as computig possibilities for digital systems, the requiremets, as for aalogue electroic systems, have chaged. Oe of them is as large as possible degree of itegratio with decrease of the umber of ecessary additioal exteral elemets, at the same time. Those requiremets ca be met by trasferrig may fuctios performed by the circuit to its iterior, icreasig its versatility ad simultaeously icreasig the umber of termials used for commuicatio with the eviromet. additio, these circuits should, i easy way, cooperate with digital systems i order to eable tuig or programmig their parameters by meas of aalogue keys. The example of such circuit ca be a multiple output curret operatioal amplifier (MOCOA). t is a
96 Topór-Kamiński L. modified covetioal curret operatioal amplifier whose umber of outputs is icreased. ts symbol is show i Fig. ad it is described by the followig depedece: Pk Nk = K = () for K. t is assumed that the umber of reversible P ad o-reversible N outputs is the same, so it is a -outputs curret operatioal amplifier. W MOCOA W K P P P N N N Fig. Symbol of multiple-output curret operatioal amplifier ts simplified realisatios i form of itegrated systems made i CMOS techiques ca be a developmet of circuit coceptio applied for the umber output blocks (Fig. ). U W P N P N B -U Fig.. Simple practical realisatio of MOCOA i CMOS techiques The MOCOA ca be also realised usig other types of electroic amplifiers e.g. classic OA-s, curret coveyors or amplifiers with a curret feedback amplifier (Fig. 3). The MOCOA eables, i a easy way, realisatio of curret amplifiers of low iteger or fractioal values of amplificatio without usig additioal exteral elemets. This ca be realised by applyig output sigals to the selected umber of outputs ad the feedback to the determied umber of other outputs. No-used outputs are coected to the referece termial havig zero potetial. The switchig of output termials ca be performed by meas of aalogue key sets cotrolled by a digital sigal D m (d,d...d m ) = (Fig. 4), where symbol deotes the umber of keys coectig the amplifier outputs to the iput termial.
Molecular ad Quatum Acoustics vol. 7, (6) 97 CC CC CC P P R R R W K = R /R N N CC CC Fig. 3 Realisatio MOCOA o the curret coveyor basis a) S OUT b) δ NP -δ S -δ S δ d d δ D NP δ D OUT S d OUT OUT Fig. 4 Aalogue key set cotrolled by digital sigals. GENERAL CONCEPTON OF THE OSCLLATOR WTH ONE MOA Basig o a curret amplifier with digitally cotrolled amplificatios, which is costructed o the oe MOCOA, ca realise a oscillatio circuit show i Fig. 5. Assumig that the blocks T ad T of the circuit is described by the secod order trasmittaces: T a T () s bs b T a s T (3) s bs b the whole circuit is described by the characteristic equatio: α T s) T ( ) = (4) ( s
98 Topór-Kamiński L. MOCOA T K α T T T T Fig. 5 Geeral coceptio of the oscillator with oe MOCOA which, takig ito accout the relatioships () ad (), ca be preseted as follows: s b a ) s ( b αa ) = (5) ( Basig o the above equatio, the coditio of oscillatio (CO) takes the followig form: b = a (6) ad the frequecy of oscillatio (FO) has the followig value: f α = b a (7) π So, the CO ad FO ca be digitally tued by meas of the coefficiets ad α. The tuig step ca be set by the coefficiet. f the suggested oscillator is to be a circuit with oe MOA, its block T ad T should be a passive circuit of RLC or RC type. 3. OSCLLATOR WTH PASSVE CRCUT RC Secod order curret trasmittaces i a passive circuit ca be also obtaied i more complicated resistaces/capacitace circuit RC. t is composed of iput low-pass filter R C ad two output filters: low-pass ad high-pass filters composed of R C elemets. Curret is iput sigal for T (s) trasmittace ad curret for T (s) trasmittace. That is why after a coectio to it digitally cotrolled MOA i the way preseted i Fig. 6, a oscillator described by the followig depedeces:
Molecular ad Quatum Acoustics vol. 7, (6) 99 T α T ( sr C )( sr C ) (8) from =, ad: T src T ( sr C )( sr C ) (9) from = is obtaied. A characteristic equatio has the followig form: s ( RC RC ) RC s R C R C α R C R C = () Hece, a coditio of oscillatio (CO) ad frequecy of oscillatio (FO) is the followig: RC R C ( ) = () ω = α R C R C () MOCOA K α C R R C CF R C T Fig. 6. Oscillator with oe MOCOA with RC passive circuit ad additioal curret follower order to verify a coceptio of oscillators with MOCOA simulatios for the circuit i Fig. 6 for R =R =kω, C =C =3.F as well which are preseted above. The models of a ideal amplifier of MOCOA type, have bee applied there. The impact of parameter value chage i the waveform of amplifier output sigal, has bee ivestigated which has bee preseted i Fig. 7.
3 Topór-Kamiński L. a).8 (t) [ma] b). (t) [ma].4. -.4 -. -.8 -. c) (t) [ma] (t) [ma].. d)..6 -.6 -. -. -. Fig. 7. Waveform of MOCOA output sigal for: α = -3 ad = (a), = (b), = 3 (c), α = -4 ad = (d) 5.CONCLUSON Multiple output curret operatioal amplifier due to its developed iteral structure i relatio to classic curret amplifier is the very versatile circuit. t eables the realisatio of circuits which are more complicated ad havig ew properties but usig less umber of additioal exteral elemets. Oscillators havig digitally tued parameters are adequate examples there. The prelimiary aalysis show that it ca be applied i high stable acoustical geerators. REFERENCES. Kaulberg T., A CMOS curret-mode operatioal amplifier. EEE Joural of Solid-state Circuits. vol. 8. No. 7, July 993.. Mucha., Curret operatioal amplifier: basic Architecture, properties, exploitatio ad future. Aalog tegrated Circuits ad Processig. No. 3, 995. 3. Koli K., Haloe A..: CMRR Ehacemet Techiques for curret-mode istrumettatio amplifiers. EEE Tras. o. Vol. 47. No. 5. May. 4. Topór-Kamiński L., Curret operatioal amplifier coceptio ad properties, SUT Publishers, Elektryka, Gliwice, vol.67, (i polish)