• An oscillator will operate at that frequency for which the total phase shift introduced,as thesignal proceeds from the input terminals,through the amplifier and feedback network and back again to the input is precisely 0 or 360 or multiple integrals of 360.
• At the oscillator frequency,the magnitude of the product of open loop gain of the amplifer A and the feedback factor ß is equal to or greater than unity.

$|\ A\beta\ | \geq1 $

the product Aß is called as the "loop gain"