Question

For an oscillator circuit to start running, what two conditions are necessary?

a. The forward gain (sometimes shown as A) must be at least 10
b.The gain-feedback product, sometimes shown as AB, must be >1
c. The phase shift around the feedback loop must be 0,360,720,… etc.
d. The feedback portion of the circuit must invert the signal

Answer 1

An oscillator circuit requires a gain-feedback product greater than 1 and a net phase shift in multiples of 360 degrees around the feedback loop to begin operating. A high quality factor with minimal damping favors a sharp resonance peak.

Step-by-step explanation:

For an oscillator circuit to start operating correctly, specifically a simple harmonic oscillator like an LC circuit, two key conditions must be met:

1. The gain-feedback product, commonly denoted by AB, must be greater than 1. This ensures that the loop gain is sufficient to sustain oscillations.
2. There must be a net phase shift of 0, 360, 720 degrees, etc., around the feedback loop. This condition ensures that the feedback signal reinforces the oscillations rather than suppresses them.

For a driven oscillator to resonate at a particular frequency, having as little damping as possible is also ideal to obtain a high-quality factor, which describes the narrowness of the resonance peak. The frequency of an LC oscillator circuit is determined by the inductance (L) and capacitance (C) values, according to the formula ω=1/√(LC), where ω is the angular frequency.