How to remove a DC offset?

[capital_zach]

Hi guys,
I have a square wave that have a dc offset approximately 1.5V. The frequency of this square wave is 10kHz. I've read that I can remove the DC offset by using high pass. My question is, what values should R and C have so that I can get a square wave with dc bias = 0V?

 

[Jack// ani]

FYI, you remove DC offset by high pass filter.

 

[capital_zach]

FYI, you remove DC offset by low pass filter.

Is it true?? I read in wiki and others said using high pass filter.

 

[Jack// ani]

Is it true?? I read in wiki and others said using high pass filter.

Oops, my bad!! Of course its HPF, sorry, I was thinking something else and this accidentally slipped in!

Correction made.

 

[capital_zach]

Oops, my bad!! Of course its HPF, sorry, I was thinking something else and this accidentally slipped in!

no problem. Do you know which value should I use for R and C??

 

[FvM]

FYI, you remove DC offset by low pass filter.

A high pass seems O.K. to me.

My question is, what values should R and C have so that I can get a square wave with dc bias = 0V?

You have to choose both the high pass characteristic impedance and time constant.

The impedance should be choosen according to the source and load impedance, that hasn't been said. I assume, that a value of 1K may be suitable.

For the time constant, two constraints exist. A too low timeconstant will result in a slope of the square wave top. For < 1% slope, the time constant T must be > 100 half periods (T> 5 ms). A larger time constant won't hurt, unless the initial startup time isn't too long. Required C = T/R.

 

[capital_zach]

A high pass seems O.K. to me.

You have to choose both the high pass characteristic impedance and time constant.

The impedance should be choosen according to the source and load impedance, that hasn't been said. I assume, that a value of 1K may be suitable.

For the time constant, two constraints exist. A too low timeconstant will result in a slope of the square wave top. For < 1% slope, the time constant T must be > 100 half periods (T> 5 ms). A larger time constant won't hurt, unless the initial startup time isn't too long. Required C = T/R.

Thank you for your description. It is easy to understand. Before this I don't really know why the time constant is that important. Thank you again.

 

[Jack// ani]

And there one online calculator which might come in handy: Guitar Pedals: R-C Filter Calculator

 

[capital_zach]

And there one online calculator which might come in handy: Guitar Pedals: R-C Filter Calculator

Thanks..very helpfull

 

[capital_zach]

Hi guys,
I've another question. I have a signal(I attached it below) and want to add an offset to it. Right now the signal have a dc bias=30mV. How can I add a dc offset to this signal to make it have a dc bias=3V?

 

[Jack// ani]

You've to use op-amp level shifter to achieve that.

Here is one such example: Non-Inverting Op-Amp Level Shifter you can tweak it to adapt for your design.

 

[capital_zach]

You've to use op-amp level shifter to achieve that.

Here is one such example: Non-Inverting Op-Amp Level Shifter you can tweak it to adapt for your design.

Thank you for the tips.. I'll try it