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Design >> Analog Design >> High-pass filter having poor ECG transient response
https://designers-guide.org/forum/YaBB.pl?num=1332444134

Message started by gido on Mar 22^nd, 2012, 12:22pm

Title: High-pass filter having poor ECG transient response
Post by gido on 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

Title: Re: High-pass filter having poor ECG transient response
Post by gido on 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

Title: Re: High-pass filter having poor ECG transient response
Post by wave 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

Title: Re: High-pass filter having poor ECG transient response
Post by gido on Mar 22^nd, 2012, 2:07pm

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

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.