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# Vivek

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### Vivek

1. 1. SINE WAVE GENERATOR USING OPAMP/IC 5551|Page
2. 2. INTRODUCTIONOscillators are circuits that produce specific, periodic waveforms such as square, triangular sawtooth, and sinusoidal. They generally use some form of active device, lamp, or crystalsurrounded by passive devices such as resistors, capacitors, and inductors, to generate theoutput.Sinusoidal oscillators consist of amplifiers with external components used to generateoscillation, or crystals that internally generate the oscillation. The focus here is on sine waveoscillators, created using operational amplifiers op amps.Sine wave oscillators are used as references or test waveforms by many circuits. A pure sinewave has only a single or fundamental frequency—ideally no harmonics are present. Thus, asine wave may be the input to a device or circuit, with the output harmonics measured todetermine the amount of distortion.2|Page
3. 3. CIRCUIT DIAGRAM FOR SINE WAVE GENERATORTwin-T oscillators A twin-T network between the output and input of an inverting op-amp, as shown in Fig .Thetwin-T network comprises R1-R2-R3-R4 and CI-C2-C3. In a "balanced" circuit, thosecomponents are in the ratios R1 = R2 = 2(R3 + R4), and Cl = C2 = C3/2. When the network isperfectly balanced, it acts as a notch filter that gives zero output at a center frequency (f0), afinite output at all other frequencies, and the phase of the output is 180° inverted. When thenetwork is slightly unbalanced by adjusting R4, the network will give a minimal output at fo.By critically adjusting R4 to slightly unbalance the network, the twin-T gives a 180° invertedphase shift with a small-signal fo. Because the inverting op-amp also causes a 180° input-to-output phase shift, there is zero overall phase inversion as seen at the inverting op-amp input,and the circuit oscillates at a center frequency of 1 kHz. In practice, R4 is adjusted so thatoscillation is barely sustained, and under that condition the sine wave has less than 1%distortion.3|Page
4. 4. COMPONENTS USED:- SR NO COMPONENT RATING 1. Capacitor .01uf,.01um,.02uf C1,C2,C3 2. Op amp Ic1 LM741 3. Power supply 9V 4. Resistors 15K,15K,6.8K,1K,27K,10K R1&R2&R3&R4,R5WORKING OF SINE WAVE GENERATORop-amp can be made to oscillate by feeding a portion of the output back to the input via afrequency-selective network, and controlling the overall voltage gain.For optimum sine-wave generation, the frequency-selective network must feed back an overallphase shift of zero degrees, while the gain network provides unity amplification at the desiredoscillation frequency. The frequency network often has a negative gain, which must becompensated for by additional amplification in the gain network, so that the total gain is unity.4|Page
5. 5. If the overall gain is less than unity, the circuit will not oscillate; if the overall gain is greaterthan unity, the output waveform will be distorted.Op-amp oscillators are circuits that are unstable—not the type that are sometimesunintentionally designed or created in the lab—but ones that are intentionally designed toremain in an unstable or oscillatory state. Oscillators are useful for generating uniform signalsthat are used as a reference in such applications as audio, function generators, digital systems,and communication systems.Two general classes of oscillators exist: sinusoidal and relaxation. Sinusoidal oscillators consistof amplifiers with RC or LC circuits that have adjustable oscillation frequencies, or crystals thathave a fixed oscillation frequency. Relaxation oscillators generate triangular, sawtooth, square,pulse, or exponential waveforms, and they are not discussed here.Op-amp sine-wave oscillators operate without an externally-applied input signal. Instead, somecombination of positive and negative feedback is used to drive the op amp into an unstablestate, causing the output to cycle back and forth between the supply rails at a continuous rate.The frequency and amplitude of oscillation are set by the arrangement of passive and activecomponents around a central op amp.Op-amp oscillators are restricted to the lower end of the frequency spectrum because op ampsdo not have the required bandwidth to achieve low phase shift at high frequencies.Voltage-feedback op amps are limited to a low kHz range because their dominant, open-looppole may be as low as 10 Hz. The new current-feedback op amps have a much widerbandwidth, but they are very hard to use in oscillator circuits because they are sensitive tofeedback capacitance. Crystal oscillators are used in high-frequency applications up to thehundreds of MHz range.APPLICATIONS:-5|Page