How does LC phase shift oscillator work?

In summary, a LC phase shift oscillator is a circuit consisting of an op-amp, LC loop, and resistors. The op-amp has a reference voltage applied to the non-inverting end and the inverting end has a feedback resistor and Vout from the LC loop connected. The circuit works by using the 180 degree phase shift from the LC loop and 60 degree phase shift from the RC circuit to produce oscillation at a frequency determined by the resonance of the LC circuit. This is different from a CR combination, which is a phase shift oscillator and uses 60 degree phase shifts in each section.
  • #1
Neyolight
15
0
Heya Everyone :blushing:

Im slightly confused as to how LC phase shift oscillator work ?

Its a circuit consisting of 1 op-amp ( used as oscillator), 1 LC loop, few resistors. The op-amp has a reference voltage applied to the non-inverting end (+ve).

The inverting end has a feedback resistor and the Vout from the LC loop connected. It looks something like this, except replace the 3RC with 1 LC - http://www.play-hookey.com/oscillators/phase_shift_oscillator.html

Ok so whatever I've read on the internet- 1LC circuit has 2 poles ( not sure what that means ) ,thus it contributes up to 180 degree phase shift per pole pair. RC circuit has a 60 degree phase shift and hence we require 3 of them !

Now, oscillation occur at the frequency were the total phase shift through 1 LC or 3 RC is 180 degree ( WHY?)

Could someone please explain to me how this works? As I am totally LOST !:confused:

Thanks :smile:
 
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  • #2
The CR combination is a PHASE SHIFT oscillator, each section is designed to give 60 phase shift and therefore a total of 180 for oscillation.
An LC oscillator is a RESONANCE oscillator. At a frequency determined by Xc =Xl resonsnce occurs and it is this frequency that is amplified to be the oscillator frequency
 

1. How does an LC phase shift oscillator generate a sine wave?

The LC phase shift oscillator works by using a combination of inductors (L) and capacitors (C) to create a feedback loop. This feedback loop causes the circuit to oscillate at a specific frequency, which results in a sine wave output.

2. What is the role of the phase shift network in an LC phase shift oscillator?

The phase shift network in an LC phase shift oscillator is responsible for creating a 180-degree phase shift between the input and output signals. This phase shift is crucial for the oscillation to occur and for the circuit to produce a sine wave output.

3. How do the values of L and C affect the frequency of the output signal in an LC phase shift oscillator?

The frequency of the output signal in an LC phase shift oscillator is determined by the values of the inductors and capacitors used in the circuit. The higher the values of L and C, the lower the frequency of the output signal will be, and vice versa.

4. What is the significance of the feedback loop in an LC phase shift oscillator?

The feedback loop in an LC phase shift oscillator is essential for maintaining the oscillations in the circuit. It ensures that the output signal is fed back to the input with the correct phase shift, allowing the circuit to sustain the oscillations and produce a continuous sine wave output.

5. How does the transistor play a role in an LC phase shift oscillator?

The transistor in an LC phase shift oscillator acts as an amplifier, boosting the signal from the phase shift network and feeding it back into the circuit. This amplification is necessary to compensate for any energy lost in the feedback loop and to maintain the oscillations in the circuit.

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