# Where is the dc component?

So a ac filter doesnt allow the dc component to pass through it, so the dc component would take a altetnative path where as the ac component would easily pass through it. My question is, where is dc component in the input wave?

• It depends on what kind of signal. Every kind of signal can be represented by a sum of sine, cosine and a DC component. – Long Pham Sep 11 '18 at 14:26
• I'm not sure I understand the question, but if the filter blocks DC, then it doesn't "go" anywhere. It simply appears across whatever component inside the filter that's doing the blocking, such as a capacitor. – Dave Tweed Sep 11 '18 at 14:49
• @LongPham, to be more precise, every periodic signal can be decomposed into a sum of sinusoids and a DC component. Finite, non-periodic signals can be approximately understood by pretending that they were snipped from an infinitely long periodic signal. – user197845 Sep 11 '18 at 14:57
• @besmirched: To be even more precise, nonperiodic signals can be represented with sines and cosines if you allow an infinite number of them. The Fourier Transform does not require periodicity. – Dave Tweed Sep 11 '18 at 15:04
• @DaveTweed I dont know anything about fourier series etc... It will probably start next semester... So you are saying the input sine wave can be expressed as a sum of trig terms, and as we approach infinity the graph of the terms become flatter and flatter? ie a dc component? – Manav Shetty Sep 11 '18 at 17:31

## 1 Answer

DC component is the average amplitude over a cycle time period of the signal. So, basically in simple terms you can call the DC component as the bias given to an oscillating signal. For a sinusoidal signal with no bias it would be 0.