Basic Principles of SinusoidalOscillator Nonlinear amplitude control> To ensure that oscillations will start, the Aβ isslightly greater than unity.> As the power supply is turned on, oscillationwill grown in amplitude.> When the amplitude reaches the desired level.the nonlinear network comes into action andcause the Aβ to exactly unity.Microelectronic Circuits
Microelectronic Circuits Basic Principles of Sinusoidal Oscillator ⚫ Nonlinear amplitude control ➢ To ensure that oscillations will start, the Aβ is slightly greater than unity. ➢ As the power supply is turned on, oscillation will grown in amplitude. ➢ When the amplitude reaches the desired level, the nonlinear network comes into action and cause the Aβ to exactly unity
The implementation of the nonlinearamplitude-stabilization mechanism The first approach makes use of a limitercircuitThe other mechanism for amplitude controlutilizes an element whose resistance canbe controlled by the amplitude of theoutput sinusoid.Microelectronic Circuits
Microelectronic Circuits The implementation of the nonlinear amplitude-stabilization mechanism ⚫ The first approach makes use of a limiter circuit ⚫ The other mechanism for amplitude control utilizes an element whose resistance can be controlled by the amplitude of the output sinusoid
A Popular Limiter Circuit for AmplitudeControl+VWhenviisclosetozero:RDiDi,D,is off v文R,RRiRRR;M0ONORR,+ R+ R?RR4RNBR+ RsR+RD2RVaMicroelectronicCircuits
Microelectronic Circuits A Popular Limiter Circuit for Amplitude Control 4 5 5 4 5 4 2 3 2 2 3 3 1 1 , 2 is off, R R R v R R R v V R R R v R R R v V v R R D D v B o A o I f o + + + = − + + + = = − When vi is close to zero:
A Popular Limiter Circuit for AmplitudeControl+VWhenvigoespositive,D1ison,D2isoffRDi文RRRM1DRRRR2MonthecontraryOvORRMR+VLR.R.NBD2RVaMicroelectronicCircuits
Microelectronic Circuits A Popular Limiter Circuit for Amplitude Control 3 3 2 2 4 4 5 5 1 on the contrary: 1 D D R R L V V R R R R L V V R R − + = − − + = + + When vi goes positive,D1 is on, D2 is off
A Popular Limiter Circuit for AmplitudeControlVOAVOAVR4SlopeSlope=Ri(R,llR.)RiRR,R0Ur0UR,SlopeRRRRVSlopeR?R.RsL(R,lR)SlopeRi(c)(b)>Transfercharacteristicofthelimitercircuit:>When R,is removed, the limiter turns into a comparator with thecharacteristicshownMicroelectronicCircuits
Microelectronic Circuits A Popular Limiter Circuit for Amplitude Control ➢Transfer characteristic of the limiter circuit; ➢When Rf is removed, the limiter turns into a comparator with the characteristic shown. = + + = − − + + − 5 4 5 4 2 3 2 3 1 1 R R V R R L V R R V R R L V D D