Test: Introduction to Oscillators

Oscillators are used for generating AC voltage. They are often characterized by the frequency of the oscillations produced. There are two main types of electronic oscillators, linear/harmonic and nonlinear/relaxation oscillator.

Negative resistance are incorporated in oscillator for sustained oscillation. Negative resistance will cancel the damping by positive (normal) resistance.

The primary trigger for oscillation is obtained from noise voltage.

Output of a stable oscillator have constant amplitude and frequency. A common criteria is the Barkhausen stability criteria, wherein it states that loop gain should be unity and feedback should be positive.

In an oscillator if phase of feedback is same as that of oscillation waveform then feedback is called positive feedback.

An oscillator is an amplifier with positive feedback. It usually has a noise which is an amplifier as an oscillating output. They do not require any type of specific input to function properly.

The input or output impedance of an amplifier with positive feedback applied, can be negative. When loop gain is greater than 1, the input impedance is a negative value, over a linear range. These are also called active resistors.

The Ac power of output signal is obtained by DC biasing voltage of amplifier.

Output of a stable oscillator have constant amplitude and frequency.

The output of the oscillator will not depend upon input voltage. There is no input voltage for an oscillator.