Simulate reactance LC tank

[advark]

Hi, can anyone help me with this:

I'm trying to simulate the reactancia of a paralel LC circuit, i want to  put in a grafic  (Reactance vs Frequency) the reactance oe the paralel LC circuit  when i  insert a sinusoidal signal.

How can ai start, any tips

Regards David

[smercurio_fc]

Well, reactance is the imaginary part of impedance, and for an LC circuit, the impedance is all imaginary (assuming ideal components). Thus, you can simply calculate the reactance as a function of L, C, and frequency. You can get the exact equation from wikipedia:

[EBL]

Here's a simple VI that calculates the impedance of a capacitor, inductor, and resistor all in parallel. If you don't want the resistor, just make its value very large.

Hope this helps,
Ed

[lmtis]

Hi Ed,
could  I trouble you to post your VI saved as LV8.0?

Thanks,

[EBL]

No problem. Here it is in 8.0.

Ed

[RnDMonkey]

Should Impedance go down at the resonant frequency of parallel LC? Like at 2.013 MHz for 2.5 µH and 2.5 nF?

[EBL]

In a parallel circuit at its resonant frequency, the magnitude of the impedance will be at maximum since the respective reactive currents in the inductor and the capacitor cancel, leaving only the conduction of the resistor. As a mathematical consequence, since all the imaginary currents cancel, the impedance is purely real; hence the imaginary component of the impedance goes to zero as the frequency approaches resonance.

If, however, there is no resistor in parallel with the L and C, the magnitude of the impedance goes to infinity at resonance and its phase is undefined.

Ed

[RnDMonkey]

That's what I thought. The reactance should go from Capacitive to Inductive, or vice versa when it crosses the resonant frequency. Nice VI. 🙂

[lmtis]

Handy tool.  Thanks Ed.