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Message started by Turin on Aug 30^th, 2010, 3:19am

Title: For anypne tha has any experience on ads...
Post by Turin on Aug 30^th, 2010, 3:19am

I'm trying to simulate a simple passive circuit (lowpass eliptical filter) but i don't seem to get that right result in the simulation.I tried some thing but still it does not seem to work. I'm just asking if anyone here see sth that i'm missing and don't do right.

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Also irrelevant to the first question can someone explain in the ideal OpAmp in the ADS2004 library what does pins 4 and 5 are for nad how are they used?(last pic)

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Thanks

Title: Re: For anypne tha has any experience on ads...
Post by pancho_hideboo on Aug 30^th, 2010, 4:39am

Turin wrote on Aug 30^th, 2010, 3:19am:

I'm trying to simulate a simple passive circuit (lowpass eliptical filter)
but i don't seem to get that right result in the simulation.

Before using simulator, can you understand filter theory correctly ?

Cutoff frequency of your LPF is 1Hz, isn't it.
However you set start frequency of AC analysis as 1kHz.

Set AC analysis like followings.
Start=0.01Hz
Stop=10KHz
Log Sweep=21pts/dec

Set x-axis as logscale in graph plot

Turin wrote on Aug 30^th, 2010, 3:19am:

Also irrelevant to the first question can someone explain in the ideal OpAmp in the ADS2004 library what does pins 4 and 5 are for nad how are they used?(last pic)

What on earth do you mean by "nad" ?

See http://edocs.soco.agilent.com/display/ads2009/OpAmpIdeal+%28Ideal+Operational+Amplifier%29
It is very clear for meaning of pin-4 and pin-5.

BTW, why don't you use following ?
http://edocs.soco.agilent.com/display/ads2009/OpAmp+%28Operational+Amplifier%29

Title: Re: For anypne tha has any experience on ads...
Post by Turin on Aug 31^st, 2010, 2:54am

Actually the filter is 1Mhz...At least according to the book I took the parameters from.

And the nad is a typo...I mean and....

I Want to use an ideal opamp to do some comparisons....

Thanks man...

Title: Re: For anypne tha has any experience on ads...
Post by pancho_hideboo on Aug 31^st, 2010, 5:52am

Turin wrote on Aug 31^st, 2010, 2:54am:

Actually the filter is 1Mhz...
At least according to the book I took the parameters from.

It can never be fc=1MHz.

Surely consider values of L and C in your filter.

For example, L=0.8255H, C=0.399F for parallel LC tank in your filter.
So attenuation pole frequency is located around f0=1/(2*pi*sqrt(L*C))=0.277Hz.

I think cutoff frequency of your LPF is 1/(2*pi)=0.16Hz.

See attached figure.
Transfer function of your filter circuit shows LPF charactereristics with attenuation pole at 0.268Hz actually.

Before using simulator, learn very very very very very very very very basic theory of filter circuits surely.

Title: Re: For anypne tha has any experience on ads...
Post by pancho_hideboo on Sep 2^nd, 2010, 8:15am

Attached figure is a comparison between Hv(Conventional Voltage Transfer Function) and S21.

You have to use S21 for characterization of LC filter.

Title: Re: For anypne tha has any experience on ads...
Post by Turin on Sep 8^th, 2010, 9:42am

Thanks for the help!