AC+DC signal equation=> Then Filter AC signal= output only DC signal visible

**sandhi** · Nov12-09, 08:08 AM

Dear friends,

I would like to know how can I remove an AC signal from a signal which is combination of AC+DC. AC signal 60V/50Hz DC=50V.

Please suggest me a C code or any algoritham or a filter which can remove AC signal completely and I should be able to see only DC signal in the out put.

with best regards,
Sandhi :(

**vk6kro** · Nov14-09, 09:24 PM

You would not be able to filter out the 60 Hz component.

The AC input of 60 volts would overdrive the amplifier and the gain of 3.9 would make it worse if that was possible. The output would just be a 50 Hz square wave

If you had an input of 0.6 volts, it may be possible to reduce the AC component in the output, but not remove it completely. You could put a large capacitor to ground after the 10 K resistor.
Try 25 uF.

**sandhi** · Nov16-09, 07:55 AM

I am sorry to tell that I have mentioned wrong value. It is 5V/1Hz Ac signal and 12 V DC signal.

**vk6kro** · Nov16-09, 10:01 AM

The 1 Hz signal would make things difficult, but there is a bigger problem.

12 volts DC into an amplifier with a gain of -3.9 will give an output of -46.8 volts.

Now, unless you have a supply of +/- 50 volts this is going to overload your amplifier.

Apart from that, filters for 1 Hz are not really practical. You can do calculations and design a filter, but the component values will become very large and expensive.