Crystal Oscillators - Equivalente circuit

Crystal Oscillators – Equivalente circuit

The Crystal Oscillators A quartz crystal has a property called: piezoelectric effect. This effect causes, by applying a mechanical pressure on the surface of the crystal, that a voltage is developed on the opposite sides. In a similar manner, a voltage applied on the faces of the crystal produces a mechanical distortion on their surface. An AC voltage causes mechanical […]

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LC Oscillator

LC Oscillator

LC oscillator: Inductance – Capacitance Oscillator A simple oscillator can be built with an amplifier stage and an inductive-capacitive network (LC) to provide an offset of -180° The oscillation frequency can be freely adjusted or tuned on a range of frequencies from 100kHz to a few hundred MHz by changing only the value of C or L. These LC […]

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Phase Shift Oscillator

Phase Shift Oscillator

The Phase Shift Oscillator The phase shift oscillator, whose basic structure is described in the picture 1.a  has a a negative gain amplifier (-K) and a feedback network consisting of a third order RC section in cascade. The oscillation condition requires that the feedback network produce a phase shift of 180° to be consistent with the negative gain amplifier which […]

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Wien-bridge Oscillator with Op Amp

Wien-bridge Oscillator with Op Amp

Wien-bridge Oscillator using Op-Amp The Wien-bridge oscillator, as shown on the basic outline of the diagram below, consists of an Operational Amplifier (OA) in a non-inverting configuration with gain 1+R2/R1 and a RC feedback network with the following transfer function: Where: Combining the first and the second equation we get: The loop gain (BA) is: The Barkhausen criterion […]

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Nonlinear Amplitude Control of a Sinusoidal Oscillator

Nonlinear Amplitude Control of a Sinusoidal Oscillator

Nonlinear Amplitude Control of a Sinusoidal Oscillator In any practical oscillator, the loop gain (ßA) must be slightly greater than unity to prevent that the tolerance parameters of components, aging, temperature effects, etc., make that ßA<1 and the circuit not meet one of the oscillation conditions specified in the equation: In which case the circuit will […]

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Sinusoidal oscillator (basic structure)

Sinusoidal oscillator (basic structure)

Basic structure of the sinusoidal oscillator The sinusoidal oscillator basic structure consists of an amplifier (A) and a selective frequency network (ß) connected in a positive feedback loop as shown in the block diagram below. Although in an oscillator, there is no input signal, it is possible to obtain the loop gain of a the amplifier (Af) which, […]

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Sinusoidal oscillators - Basic principles

Sinusoidal oscillators – Basic principles

Sinusoidal Oscillators Sinusoidal oscillators play an important role in electronic systems that use harmonic signals. Despite that, in many instances are known as linear oscillators, it is necessary to use some non-linear feature to generate a sine wave output. In fact, the sinusoidal oscillators are essentially non-linear which complicates the technical design and analysis of such circuits. The […]

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