# Need help understanding tank circuits

Discussion in 'General Electronics Chat' started by qpotential, Mar 29, 2009.

1. ### qpotential Thread Starter New Member

Mar 29, 2009
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I would like to make a parallel tank circuit using a variable capacitor (for frequency control) and a high efficiency inductor. I am going to use the tank inductor as an I-core solenoid to utilize its magnetic field. I'd like to use this in a parallel tank configuration so that the energy in the tank can be used over and over again in the solenoid and only the tank losses will have to be supplemented by the power source. This is to ensure that the output field remains high but the input energy requirements can be significantly reduced.

I have seen many statements that say (and diagrams showing) there needs to be an "active component" present or an AC power source, otherwise the tank will not oscillate. I would like to go with the AC power source instead of an "active component" because it seems to be the simplest from a design perspective.

Does the frequency of the AC source have an effect on the tank frequency? If I do have to use an "active component", what would be the simplest and most efficient means of doing so with the consideration that this tank will not have any electrical load applied to it?

The only end goal I have is to make an LC tank oscillate using the fewest components possible. I am targeting the 20Hz to 240Hz range, if that helps any.

Thanks,
Mike

2. ### thatoneguy AAC Fanatic!

Feb 19, 2009
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A tank circuit is a "Notch Filter", there is one frequency where the impedance of the capacitor and inductor are both at their peak. Above that frequency the inductor will block, capacitor will pass, below that frequency, the capacitor will block, inductor will pass.

When this is used in a feedback amplifier, that frequency is where it will oscillate. Too high or too low frequency feedback will "push" the oscillator back towards the highest impedance "notch"

3. ### qpotential Thread Starter New Member

Mar 29, 2009
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Last edited: Mar 29, 2009