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gido Junior Member Offline Posts: 23	High-pass filter having poor ECG transient response Mar 22^nd, 2012, 12:22pm Hello, I have designed a fully differential passive high-pass filter for ECG and in running the transient response, I get the common mode to be decreasing and settling at a longer time. How best can i resolve this? ( make the common mode zero)..... Attached is the fully differential transient response. Thanks
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gido Junior Member Offline Posts: 23	Re: High-pass filter having poor ECG transient response Reply #1 - Mar 22^nd, 2012, 12:24pm Pls attached too is the schematic of the passive fully-differential high-pass filter. I subtract the voltages at the two outputs to get the response
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wave

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Re: High-pass filter having poor ECG transient response
Reply #2 - Mar 22^nd, 2012, 1:45pm

With limited information, this seems fundamental. �
Single HPF have settling times and a differential step on a pair may have asymmetry. �
Is your input DC same as output CM (0V) ?
Are your waveforms DC balanced?

You might want to plot single ended inputs, with DC content.
How to you plan to amplify this?

Wave

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gido

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Re: High-pass filter having poor ECG transient response
Reply #3 - Mar 22^nd, 2012, 2:07pm

wave wrote on Mar 22^nd, 2012, 1:45pm:

With limited information, this seems fundamental. �
Single HPF have settling times and a differential step on a pair may have asymmetry. �
Is your input DC same as output CM (0V) ?
Are your waveforms DC balanced?

You might want to plot single ended inputs, with DC content.
How to you plan to amplify this?

Wave

yeah, my input DC is same as output CM(0V)
I plotted single ended transient and the DC contents are same(0V).
One thing is, the fully differential transient response for a sinusoidal input has a constant CM that is zero throughout.

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