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MFB high-pass Filter not having a unity gain (Read 2314 times)

gido Junior Member Offline Posts: 23	MFB high-pass Filter not having a unity gain Feb 25^th, 2012, 9:41am hello, I am designing a high-pass filter using the multiple feedback configuration. I am doing the AC analysis and i have tried several times but it is not giving me a unity gain (1000mV). my input voltage is 1V. I have changed op-Amp design but still no nice result. Can anyone help me here? I am running cadence. Thanks
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rfidea

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Posts: 159
Europe

Re: MFB high-pass Filter not having a unity gain
Reply #1 - Feb 25^th, 2012, 10:21am

The gain of a MFB filter is set by a resistor ratio. Please look at page 7 in the following document.

http://www.ti.com/lit/an/sloa049b/sloa049b.pdf

As a general recommendation I think you should start the filter design with an ideal opamp, use an inverting amplifier with a lot of gain. Then you will see if you have a fundamental problem with your RC networks or not. Get that to work first. It it then do not work with a real opamp, the problem is related to the opamp.

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buddypoor

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Bremen, Germany

Re: MFB high-pass Filter not having a unity gain
Reply #2 - Feb 26^th, 2012, 9:44am

gido wrote on Feb 25^th, 2012, 9:41am:

hello,
I am designing a high-pass filter using the multiple feedback configuration. I am doing the AC analysis and i have tried several times but it is not giving me a unity gain (1000mV). my input voltage is 1V.
I have changed op-Amp design but still no nice result.
Can anyone help me here?
I am running cadence.

Thanks

I suppose it shouldn't be a problem to give you some hints - but without any circuit information? What do you expect?

LvW (buddypoor: In memory of the great late Buddy Rich)

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