Electronics Forums > Re: DC Wave Questions

# Re: DC Wave Questions

John Popelish
Guest
Posts: n/a

 06-11-2005, 01:05 AM
(E-Mail Removed) wrote:
> 2 questions about a fully DC Sine Wave....let's suppose you have a DC
> Sine wave which varies from +5V to +15V peak-to-peak going into a load
> with R, L, and C components.....
>
> Question #1:
> Is the load's impedance a function of R, L, and C (and wave frequency)
> or is it simply just R (i.e. Z=R)? In other words does non-resistive
> impedance (L + C) really only matter with an AC signal OR anytime
> voltage varies periodically (even if it is all DC)?
>
>
> Question #2:
> Would a "regular" negative peak detector ciruit, like shown here:
>
> http://www.elektroda.net/cir/index/D...CTOR.htmgative
>
>
> work for the DC Wave described? Will it output +5V or do negative peak
> detectors only work for AC signals?
>
> Thank you.

According to Fourier analysis, any repeating waveform can be
decomposed into harmonically related and appropriately phase shifted
sine waves and also a DC component. If all the components involved
are linear, then they react to each of these components,
independently, and the result is the linear sum of all those
reactions. So the capacitors react to the DC component as open
circuits, and the inductors as short circuits. At all frequencies,
the resistances follow ohms law, and at each AC harmonic, the
inductances and capacitances react in their normal frequency dependent
ways.

Throw in one nonlinear component, like a diode, and you have to do a
completely different kind of analysis.

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