How to depict the operation principle of the oscillator circuit?
Crystal controlled oscillators may be considered as consisting of an amplifier and a feedback network that selects a part of the amplifier output and returns it to the amplifier input. A generalized depiction of such a circuit is shown below.
In order for an oscillator circuit to operate, two conditions must be met:
(A) The loop power gain must be equal to unity.
(B) The loop phase shift must be equal to 0,2π,4π, etc. radians
