Gyrators are usually used to create impractical inductances or frequency dependant negative resistances but I suppose you could. I do not think you would gain anything though since you would be trading one set of non-ideal behaviors for a different set. This is especially the case since the non-ideal behavior of inductors is almost always worse than the non-ideal behavior of capacitors.
For example, you can sometimes avoid large feedback or input resistances by substituting a T-network but offset voltages and voltage noise will be multiplied accordingly. On Sun, 1 Jan 2012 13:52:27 -0700 (MST), "Don Latham" <[email protected]> wrote: >Aren't there op-amp circuits that create a large capacitance? The gyrator? >Don > >David >> Jim Williams did this in one of his designs for measuring low >> frequency reference noise. The large value low leakage wet tantalum >> capacitor he used was like $400 and it took 24 hours for the >> dielectric absorption to settle: >> >> http://www.linear.com/docs/28585 >> >> You can get the necessary time constant using a good 1uF film >> capacitor with good design and construction in this case. >> >> On Sun, 1 Jan 2012 15:11:04 -0500, Bob Camp <[email protected]> wrote: >> >>>Any real world capacitor will have a dielecric with an associated >>> insulation resistance. It's a "more money gets better performance" sort >>> of thing, but there are indeed limits. A 1000 uF cap that has a "good" >>> insulation resistance number might cost you more than some new carsÂ…. >>> >>>On Dec 31, 2011, at 11:54 PM, Chris Albertson wrote: >>> >>>> On Sat, Dec 31, 2011 at 5:56 PM, Hal Murray <[email protected]> >>>> wrote: >>>> >>>>> I think the main problem in this area is building a low pass filter >>>>> with a >>>>> long time constant. >>>>> >>>>> The time constant of the filter has to be: >>>>> long relative to the noise from the phase detector >>>>> short relative to aging of the oscillator >>>>> short relative to environmental changes >>>>> (so the osc can track temperature and voltage >>>>> those changes may be in the PLL system rather than the osc) >>>>> >>>>> If we are starting with PPS (rather than 10KHz), the filter time >>>>> constant >>>>> needs to be 10s or 100s of seconds. How do I build an analog filter >>>>> with a >>>>> time constant that long? >>>>> >>>> >>>> Time constant is just R*C. If you have a 1000uF cap and a 1K >>>> resistor you >>>> have 1 second. In theory you could build 100s just by using a 100K >>>> resistor but I think real world components are not perfect enough. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
