Solution:

• Barkhausen criterion are a set of two mathematical conditions which a linear electronic circuit must follow to act as an electronic oscillator. Barkhausen’s criterion applies to linear circuits with a feedback loop.
• It cannot be applied directly to active elements with negative resistance like tunnel diode oscillators.
• The kernel of the criterion is that a complex pole pair must be placed on the imaginary axis of the complex frequency plane if steady state oscillations should take place.
• It needs to have positive feedback.
• The loop gain is at unity. That is the magnitude of the product of open loop gain and the magnitude of the feedback factor is unity.