Negative resistance is incorporated in an oscillator for sustained oscillation.

Introduction:
An oscillator is an electronic circuit that generates a periodic waveform without any external input signal. It is an essential component in various electronic systems such as radios, televisions, and communication devices. In order to sustain the oscillations, the oscillator requires a feedback mechanism that provides the necessary energy to compensate for the energy losses in the circuit.

What is negative resistance?
Resistance is a measure of how a component or a circuit element resists the flow of electric current. It is typically a positive value, meaning that it dissipates energy as heat. However, negative resistance is a special case where the voltage across a component decreases as the current through it increases. In other words, negative resistance can produce energy rather than dissipating it.

Importance of negative resistance in an oscillator:
In an oscillator circuit, energy is fed back from the output to the input to sustain the oscillations. This feedback can be achieved through passive elements like resistors and capacitors. However, these passive elements also introduce energy losses due to their inherent resistive properties. To compensate for these losses and sustain the oscillations, a negative resistance element is incorporated into the oscillator circuit.

Sustained oscillation:
Sustained oscillation refers to the continuous generation of a periodic waveform without any external stimulus. In an oscillator circuit, sustained oscillation is achieved when the loop gain of the circuit is equal to or greater than unity. The loop gain is the product of the gain of the active device in the circuit and the feedback factor.

Role of negative resistance:
Negative resistance plays a crucial role in sustaining the oscillations of the oscillator circuit. By introducing negative resistance into the circuit, the overall loop gain can be increased. This helps to compensate for the energy losses in the circuit and maintain the required loop gain greater than unity. As a result, the oscillator can generate sustained oscillations with a stable frequency and amplitude.

Conclusion:
In summary, negative resistance is incorporated in an oscillator for sustained oscillation. By introducing negative resistance into the circuit, the energy losses can be compensated, and the required loop gain can be achieved to sustain the oscillations. This ensures that the oscillator generates a stable periodic waveform without any external input signal.