# Question of possible circuit

Suppose we have an alternating signal and another signal is produced in the loop which is DC. Is there a circuit which tracks down the DC signal even if it is mixed with an AC signal?(somehow removes the AC signal from its output)

I am asking this question to find it so I can begin studying it.

• "in the loop": Which loop? Is your alternating signal a current or voltage signal? it's possible you're looking for a low-pass filter, but I'm not sure – your question is very vague. – Marcus Müller Oct 25 '20 at 17:09
• Voltage signal and I want a circuit AC blocking but not DC blocking. – Se1fie Oct 25 '20 at 17:14
• Yeah, a low-pass filter probably. Still not clear what "loop" if this is a voltage signal. – Marcus Müller Oct 25 '20 at 17:16

$$\V_{IN}\$$ would be your combined AC signal and DC level and $$\V_{OUT}\$$ would be largely free from AC artefacts but, never totally free of them. So, you have to be pragmatic and ask yourself how low an AC signal on the DC output ($$\V_{OUT}\$$) can I tolerate to achieve my goals. For instance, if the lowest frequency AC signal were 1 kHz then, if you used an inductance of 100 mH and a capacitance of 100 uF, you would find that the AC signal on $$\V_{OUT}\$$ due to the presence of 1 kHz on the input would be reduced by about 52 dB. Is this enough? Only you can say: -