Question

The phase difference produced by the active element of Hartley oscillator is __________

(a) 0 degree

(b) 180 degree

(c) 90 degree

(d) 120 degree

This question was posed to me during a job interview.

This key question is from Hartley Oscillator-2 in division Oscillators of Analog Circuits

Answer 1

The correct answer is (b) 180 degree

Explanation: The coil has a tap such that the proper phase is available to the base of the transistor. Value of L and C are adjusted to give a phase shift of 180°. The transistor itself creates a 180° phase shift and hence total shift is 360°/0.