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Old 22nd April 2004, 11:15 AM   #31
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I think I'll get the picture now, using SPICE. The last element is a resistor which will be conveted into a capacitor. It's OK to have a cap as load up to a finite frequency. Highpass fillter has a cap to "unlimited frequency => unrealistic current demands.

I'll guess that it's true that highpass filters can't be made by FDNR. In theory it will but not in real life.
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Old 26th April 2004, 04:46 PM   #32
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Quote:
Originally posted by peranders

I'll guess that it's true that highpass filters can't be made by FDNR. In theory it will but not in real life.
Here's a floating Current Conveyor, from
http://www.kemt.fei.tuke.sk/Predmety...ialy/ch029.pdf

it's in part 29.3 of the article:
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Old 27th April 2004, 01:06 PM   #33
Electrons are yellow and more is better!
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FDNR's are impossible to use a highpass filter but I can use the same style simulated inductor instead.

jackinnj, please note that your example is a simple negative resistance, not frequency dependent.
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Old 27th April 2004, 01:27 PM   #34
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Per -- no, the bottom figure is reactive.
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Old 27th April 2004, 01:34 PM   #35
Electrons are yellow and more is better!
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Yes, as L, inductance. I know how a GIC inductance looks like, just use one cap.
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Old 14th July 2005, 06:42 AM   #36
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Why not use a gyrator circuit to simulate an inductor?

I do that in my own active filter one

The manual has all equations needed

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Old 14th July 2005, 06:55 AM   #37
Electrons are yellow and more is better!
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I know about the gyrator circuit with one or two opamps but a GIC looks cooler. I have no idea if it has any hidden good properties.

Jens, how come you found this old thread? Searched for FDNR?
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Old 14th July 2005, 07:07 AM   #38
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Nope,

I just clicked your link in the bottom of your post

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Old 22nd October 2010, 02:42 PM   #39
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Default HP FDNR

I know this thread is old and dead. But in case anyone was curious you can get a FDNR HP using something like the attached image. If you want LP just switch all the R's and C's
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Old 19th February 2011, 04:42 PM   #40
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I started investigating FDNR's again.

I used a 1 op-amp grounded FDNR on my crossover page, and also a 1 op-amp grounded gyrator (inductor simulator).

One-end-is-grounded one-opamp FDNR's and gyrators use 1 opamp instead of 2, which is very useful for shunt legs on filters; its downside is it has a parasitic shunt R (in the case of the FDNR, series R in the case of the gyrator), which, with careful design, can be rendered insignificant.

I used it to great effect, reducing my opamp count, over the 2 op-amp gyrator/FDNR, and it is far less sensitive to component tolerance than the biquad type of zero-pair implementation (according to Spice Monte Carlo analysis).

With 2 opamps I achieved a 4th order elliptic filter (4 poles, 2 imaginary zero pairs). By configuring the opamp as a unity gain follower, open loop gain isn't that much of an issue, depending on the exact topology (e.g. if the impedance you need doesn't need to go very high); what you have to watch out for is the load presented to the opamp and the opamp input impedance (you usually need FET input opamps). The effect of open loop gain is apparent if you simulate gain = 0.99 (which is with open loop gain = 40 dB). (Ditto for effect of input impedance, on circuit's required max impedance).

I wrote the page back in 2000:

Jason Cuadra: Elliptic Crossovers

Scroll to the bottom.

Last edited by jasoncsbb; 19th February 2011 at 04:50 PM.
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