FDNR in active filters (Frequency Dependent Negative Resistor) - Page 3 - diyAudio
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Old 20th April 2004, 10:22 PM   #21
Electrons are yellow and more is better!
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Is this FDNR topology so rare that NOONE has come close to it? I'll guess I'll have to simulate it when I have got the time.
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Old 21st April 2004, 01:49 AM   #22
GaryB is offline GaryB  United States
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How about this?
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Old 21st April 2004, 06:57 AM   #23
Electrons are yellow and more is better!
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This is one way to solve it but "the circuit" is a simulated inductor. The weird FDNR caught my interest so I wanted to use it also. Nobody will see the difference but I will.
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Old 21st April 2004, 08:57 AM   #24
moamps is offline moamps  Croatia
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Default Re: Re: FDNR in active filters

Quote:
Originally posted by GaryB

Take a look at the PCM63 datasheet: http://focus.ti.com/lit/ds/symlink/pcm63.pdf
Hi,
Complete DAC project with PCM63 and FDNR was published in Elektor 10/92 (German version).
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Old 21st April 2004, 09:14 AM   #25
Electrons are yellow and more is better!
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Please, guys, my question now was about high-pass filters and you don't have them in CD players.
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Old 21st April 2004, 09:31 AM   #26
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Peranders wants to build a HIGHpass, so the DAC project wouldn't help him much.

You have to use an inductor to ground in order to get a highpass filter (wheter it is first-order with a series resistor or 2nd order with a series cap). This can be simulated using a gyrator or the well-known simulated inductor as it is used in many EQ circuits.

Both of these are grounded however. But I don't see any reason to use sophisticated circuitry that can be run ungrounded, only to substitute a simple cap.

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Old 21st April 2004, 09:34 AM   #27
Electrons are yellow and more is better!
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Quote:
Originally posted by peranders
I have small plans to make a really cool cross over filter. I had in mind, 2nd, 3rd and 4th order LP sub, LP, BP and HP filter. Super universal with universal charateristics, Chebushev, Butterworth, Bessel (anykind) etc.

It seems that FDNR is a totally unexplored field. Maybe we should explore it for hifi usage?
Since overkill is my brand I thought it would be cool to design a well-made ultra universal filter but this is a rather big project so I'll guess I can't make it this week. Seriously, I have thought about it 10 years now and time to time it pops up in my brain.

The opamps I think of here are AD8620 and OPA2134. The opamps have to be dual (=matched), so have I been told.
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Old 21st April 2004, 09:34 AM   #28
moamps is offline moamps  Croatia
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Quote:
Originally posted by peranders
Please, guys, my questionnow was about high-pass filters and you don't have them in CD players.

Don't be nervous....
Search for "GIC" in browser...You will find something like this......
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Old 21st April 2004, 09:35 AM   #29
Electrons are yellow and more is better!
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But this isn't a FDNR.
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Old 21st April 2004, 09:38 AM   #30
Electrons are yellow and more is better!
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Quote:
Originally posted by phase_accurate
But I don't see any reason to use sophisticated circuitry that can be run ungrounded, only to substitute a simple cap.
A possible solution is to use GIC as an inductor but the goal was (if it's possible) to have an all-FDNR filter.
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