Hi
Most generators are using LC connected in parallel. Do you know circuit of generator where LC are connected in series? Audio frequency.
LC circuits are usually used in RF oscillator circuits. Audio oscillators can use RC circuits like phase shift or Wien bridge circuits.
For an example of L C series circuits see
I know posts # 2 and 3, I don't know post #1.
I am looking for something like this, but L and C need to be connected in series.
Why?
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Usually we try to avoid this because the LC junction is floating and is very senstive to stray capacitance to ground. If there's much current it can also be at a high voltage. Why are you so keen to have them in series?
Just curious it is possible or not.
Series LC circuits have uses, as explained in the article linked in post #3.
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Yes it is but in an oscillator you would need to drive it from a voltage source and sense the current wiith a zero input impedance amplifier. Then the actual frequency is sensitive to stray capacitance at the LC junction. Active amplifier devices like mosfets look more like voltage controlled current sources which is more compatible with a parallel tuned circuit in which you can absorb stray capacitance more easily, so that is more usually used in oscillator design. Series LC circuits also arise in classic filter design methods but are very awkward ro make and sensitive to strays so one tries very hard to avoid them.
A parallel LC circuit shows maximum resistance at its resonant frequency. A series LC circuit shows minimum resistance at its resonant frequency. For an oscillator, we need to consider the phase shifts involved, not simply voltage or current.
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Conclusion = no such generator exists.
Absence of evidence is not evidence of absence.
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I could draw one easily for you using a couple of op amps and a few resistors plus an L and C but there's no particular benefit to using a series resonator.
this is not about benefits, it is about another type of generator.
In the circuit you showed, at the resonant frequency, where the impedance of the LC circuit is highest you get maximum positive feedback, and hence oscillation.
Because a series LC circuit has a minimum impedance at resonance, you would have to swap the position of the resistor and the LC circuit to get a similar effect.
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With 10mH and 33nF I have 110 kHz, should be 8.7kHz, frequency depends not only on LC but also on values of the resistors.
Thanks, it was pleasure to test that circuit.
The oscillation you observe may not have much to do with the LC circuit, especially in a case so far from the resonant frequency.
Op amp circuits tend to oscillate if they are not properly decoupled.
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You don't say what your resistor values are. The resistor from the +ve opamp input to gnd is in series with the LC circuit. The reactance of the inductor at 8.7kHz is 2 x pi x 1e-2 = 628 ohms. If that resistor had the same value the circuit Q would be unity so it's hardly "resonant" at all! The LC circuit will then have little influence on what frequency this circuit oscillates at. As I mentioned above, you need to terminate the LC with a very low impedance and drive it from a voltage source. The opamp does the second but in that configuration not the first!
Also the opamp "gain bandwidth product" is important as it helps to determine the phase shift through the amp and this can have a big effect on the oscillator frequency especially if the Q is low.
Did you test this in simulation or reality? A real 10mH inductor will have a series resistance which also limits Q, and depending on type the capacitor may not be brilliant either.
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So it's just about being different for the sake of it - despite all the disadvantages discussed?
I am using MCP6022, I play with all resistors; 10k, 100k and was not able to make oscillator frequency depends only on LC.