# Ideal LC oscillator and barkhausen criterion

1. Jun 16, 2010

### asifshaik

I am unable to relate the Barkhausen criterion for oscillations to sustain to the Ideal LC oscillator with an initial condition.
Assume you have a parallel combination of LC(both with Q=infinity) with an initial condition say V volts on capacitor. Mathematically it will oscillate with the frequency 1/2/pi/sqrt(LC). Now I see no feedback here. where you apply barkhausen criterion for the oscillations in that feedback system?

Even if there is a loss in inductor and I keep a -ve resistance in parallel to cancel out that loss, how can i apply the Barkhausen criterion for this as well.

2. Jun 16, 2010

### waht

LC isn't a feedback system. A feedback system is when a sampled output of a network is fed back its input:

Oscillators work on the principle that the resonant element is amplified with an external amplifier, and then the amplified output is fed back to its input in correct phase as established by Barkhausen's criterion in order to sustain oscillations indefinitely.

3. Jun 18, 2010

### asifshaik

Thank you very much for the reply.