A common emitter amplifier with a gain of 10 is used to design an oscillator. What should be the gain and phase shift of the feedback network for sustained oscillation? 

Barkhausen Criterion:

For an oscillator to produce sustained oscillations, the following conditions (known as the Barkhausen Criterion) must be met:

• Magnitude Condition: The product of the gain of the amplifier (A) and the feedback network (β) must be equal to 1, i.e., A × β = 1.
• Phase Condition: The total phase shift around the loop must be 0° or an integral multiple of 360°.

Given Data:

• The amplifier is a common emitter amplifier with a gain of 10 (A = 10).
• The feedback network is tasked with providing the required gain (β) and phase shift to satisfy the Barkhausen Criterion.

Analysis of the Feedback Network:

To design an oscillator using the given amplifier, the feedback network must satisfy the following:

1. The gain of the feedback network (β) must be such that A × β = 1. Since A = 10, we require β = 1/10 = 0.1.
2. The phase shift introduced by the feedback network must complement the phase shift introduced by the amplifier to achieve a total phase shift of 360° (or 0°). A common emitter amplifier inherently introduces a phase shift of 180°, so the feedback network must provide an additional 180° phase shift.

Correct Option:

Option 3: Gain = 0.1, Phase Shift = 180°