Re: gEDA-user: OFF: capacitors for RF power amplifier
On Wed, Apr 13, 2011 at 09:31:24AM +0100, Andy Fierman wrote: > If you are going to model the PA - particularly to look at resonance > effects - then you should include reasonably accurate models for the > inductors and capacitors which include their major parasitic > components. > > The Murata Chip S-Parameter & Impedance Library is a handy tool for > looking at their ceramic capacitor and inductor behaviour. > > http://www.murata.com/products/design_support/mcsil/index.html > > or there's an online version: > > http://ds.murata.com/software/simsurfing/en-us/index.html > > Andy. > > signality.co.uk > > > On 12 April 2011 23:57, Wojciech Kazubski wrote: > >> I'm currently designing a power amplifier for the HF (3-30MHz) radio > >> band. > >> > >> I am selecting capacitors for the low pass harmonic filter bank at the > >> output. > >> My question is what kind of capacitors should I use? I apply not more then > >> 100V of say 30MHz maximum. > >> > >> My best bet is to use X7R capacitors with as much DC voltage rating as I > >> can > >> get. I don't know if there's any connection between the DC and AC losses. > >> > >> > >> Thanks, > >> Levente > >> > > The biggest problem can be the current handling capacity. Very few > > capacitor makers specify this. Usually if a capacitor is rated for 100V > > this means 100V DC wthout any current. Only special purpose capacitors for > > RF power applications have HF current ratings, see Anerican Technical > > Ceramics for example: > > http://www.atceramics.com > > Another manufacturer is Dielectric Labs: http://www.dilabs.com but they are not cheap, especially the porcelain ones. However, they have very good temperature characteristics and high to very high voltage ratings. Dilabs basically only manufactures capacitors for high frequency applications. > > For RF do not use X5R/X7R (good only for supply bypassing), use NP0/C0G or > > similar low loss ones. Agreed, well X5R/X7R can be used for loop filters in PLL and servo applications, when the bandwidth is not too critical, as long as you meet the stability criteria (but I use 25 or even 50V rated capacitors when the voltage on the capacitor never exceeds 3.3V). The problem is that you can't use anything else when you have size constraints and need capacitors in the 0.1 to 10 microfarad range: very low loop bandwidths for either crystal (VCXO) oscillators and even much lower for thermal stabilization loops. On the other hand, class Y and Z dielectrics should not even be allowed; a look at temperature and voltage dependence graphs should suffice to convince any circuit designer. Gabriel ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
On Wed, Apr 13, 2011 at 1:31 AM, Andy Fierman wrote: > If you are going to model the PA - particularly to look at resonance > effects - then you should include reasonably accurate models for the > inductors and capacitors which include their major parasitic > components. > > The Murata Chip S-Parameter & Impedance Library is a handy tool for > looking at their ceramic capacitor and inductor behaviour. > > http://www.murata.com/products/design_support/mcsil/index.html > > or there's an online version: > > http://ds.murata.com/software/simsurfing/en-us/index.html > Hmm...it seems to be an .exe. Do they have a table or something? ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
If you are going to model the PA - particularly to look at resonance effects - then you should include reasonably accurate models for the inductors and capacitors which include their major parasitic components. The Murata Chip S-Parameter & Impedance Library is a handy tool for looking at their ceramic capacitor and inductor behaviour. http://www.murata.com/products/design_support/mcsil/index.html or there's an online version: http://ds.murata.com/software/simsurfing/en-us/index.html Andy. signality.co.uk On 12 April 2011 23:57, Wojciech Kazubski wrote: >> I'm currently designing a power amplifier for the HF (3-30MHz) radio >> band. >> >> I am selecting capacitors for the low pass harmonic filter bank at the >> output. >> My question is what kind of capacitors should I use? I apply not more then >> 100V of say 30MHz maximum. >> >> My best bet is to use X7R capacitors with as much DC voltage rating as I can >> get. I don't know if there's any connection between the DC and AC losses. >> >> >> Thanks, >> Levente >> > The biggest problem can be the current handling capacity. Very few capacitor > makers specify this. Usually if a capacitor is rated for 100V this means 100V > DC wthout any current. Only special purpose capacitors for RF power > applications have HF current ratings, see Anerican Technical Ceramics for > example: > http://www.atceramics.com > > For RF do not use X5R/X7R (good only for supply bypassing), use NP0/C0G or > similar low loss ones. Their maximum capacitance is limited to few nanofarads > in 1210 case, so it may be necessary to connect few in parallel to get > desired value. Also if you do not have capacitors with high current ratings, > connect several smaller ones in parallell instead of one big. > Foil type capacitors are suitable for lowest frequencies (LW/MW) and have to > be low loss. Polipropylene or teflon ones are low loss and usable, while > poliester ones are too lossy. Parasitic inductance can also be a problem. > Check your PA circuits with circuit simulator for resonance effects. In this > case currents and voltages can be much higher. > > Wojciech Kazubski > > > ___ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
> I'm currently designing a power amplifier for the HF (3-30MHz) radio > band. > > I am selecting capacitors for the low pass harmonic filter bank at the output. > My question is what kind of capacitors should I use? I apply not more then > 100V of say 30MHz maximum. > > My best bet is to use X7R capacitors with as much DC voltage rating as I can > get. I don't know if there's any connection between the DC and AC losses. > > > Thanks, > Levente > The biggest problem can be the current handling capacity. Very few capacitor makers specify this. Usually if a capacitor is rated for 100V this means 100V DC wthout any current. Only special purpose capacitors for RF power applications have HF current ratings, see Anerican Technical Ceramics for example: http://www.atceramics.com For RF do not use X5R/X7R (good only for supply bypassing), use NP0/C0G or similar low loss ones. Their maximum capacitance is limited to few nanofarads in 1210 case, so it may be necessary to connect few in parallel to get desired value. Also if you do not have capacitors with high current ratings, connect several smaller ones in parallell instead of one big. Foil type capacitors are suitable for lowest frequencies (LW/MW) and have to be low loss. Polipropylene or teflon ones are low loss and usable, while poliester ones are too lossy. Parasitic inductance can also be a problem. Check your PA circuits with circuit simulator for resonance effects. In this case currents and voltages can be much higher. Wojciech Kazubski ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
quick link to Wima tech info: http://www.wima.de/EN/technicalinformation.htm One really nice thing about plastic film caps is that they fail open. Ceramic tends to fail short - which can sometimes ruin your day :) ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
Kovacs Levente wrote: I'm currently designing a power amplifier for the HF (3-30MHz) radio band. I am selecting capacitors for the low pass harmonic filter bank at the output. My question is what kind of capacitors should I use? I apply not more then 100V of say 30MHz maximum. My best bet is to use X7R capacitors with as much DC voltage rating as I can get. I don't know if there's any connection between the DC and AC losses. Thanks, Levente I also would recommend the plastic types. Wima makes nice ones but there are others. C0G/NP0 good too, as already pointed out. gene ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
On Mon, Apr 11, 2011 at 04:55:15PM +0200, Kovacs Levente wrote: > > I am selecting capacitors for the low pass harmonic filter bank at the output. > My question is what kind of capacitors should I use? I apply not more then > 100V of say 30MHz maximum. The classic cap in this application is silver mica. High voltage capacity, super tolerance compared to other types (to 0.25%! but commonly 1% or 2%). The only ones I have are enormous bulky things with "dot" style marking. A quick search on Mouser turns up only SMT ones... > My best bet is to use X7R capacitors with as much DC voltage rating as I can > get. I don't know if there's any connection between the DC and AC losses. Not X7R. -- Ben Jackson AD7GD http://www.ben.com/ ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
> "Kovacs" == Kovacs Levente writes: Kovacs> On Mon, 11 Apr 2011 16:58:37 +0200 Uwe Bonnes Kovacs> wrote: >> What value do you need? Try NP0/COG type, even if substantial more Kovacs> 120pf ... 1.5nF In this range you will easily find better types than X7R... -- Uwe Bonnesb...@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt - Tel. 06151 162516 Fax. 06151 164321 -- ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
And one more note. On Apr 11, 2011, at 9:09 AM, Andy Fierman wrote: > The capacitance vs. voltage of the X7R dielectric is not very good. > NP0/COG are usually specified for precision timing and filter > applications. > > NP0/COG also have a much lower temperature coefficient. NPO/C0G is a temperature coefficient spec. Usually, a low temperature coefficient ceramic will also have low dielectric hysteresis. However, I have encountered exceptions. It's preferable to use capacitors where the manufacturer's data sheet gives a limit on hysteresis. A common spec for a "good" capacitor is <0.1% hysteresis. John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ j...@noqsi.com ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
On Apr 11, 2011, at 9:55 AM, John Doty wrote: > > On Apr 11, 2011, at 9:19 AM, Kovacs Levente wrote: > >> On Mon, 11 Apr 2011 16:58:37 +0200 >> Uwe Bonnes >> >> wrote: >> >>> What value do you need? Try NP0/COG type, even if substantial more >> >> 120pf ... 1.5nF > > Another possibility in that range is plastic "film" dielectrics rather than > ceramic. Oh, and one more issue. AC is much more stressful on a capacitor than DC. It's best to choose a capacitor with an AC voltage rating. If you can't, a common rule of thumb is to choose one with a DC voltage rating 3 times the AC RMS. Classically, this has been an application for mica capacitors, but they're relatively rare these days. John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ j...@noqsi.com ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
On Apr 11, 2011, at 9:19 AM, Kovacs Levente wrote: > On Mon, 11 Apr 2011 16:58:37 +0200 > Uwe Bonnes > > wrote: > >> What value do you need? Try NP0/COG type, even if substantial more > > 120pf ... 1.5nF Another possibility in that range is plastic "film" dielectrics rather than ceramic. John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ j...@noqsi.com ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
http://www.avx.com/SpiApps/default.asp Some cool capacitor tools, like spicap3 Steve On Mon, Apr 11, 2011 at 11:19 PM, Kovacs Levente wrote: > On Mon, 11 Apr 2011 16:58:37 +0200 > Uwe Bonnes > > wrote: > >> What value do you need? Try NP0/COG type, even if substantial more > > 120pf ... 1.5nF > >> expensive. I guess the X ceramic will introduce more harmonics than >> it will filter out... > > Thanx for the hint. > > -- > Kovacs Levente > Voice: +36705071002 > > > > > ___ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
On Mon, 11 Apr 2011 16:58:37 +0200 Uwe Bonnes wrote: > What value do you need? Try NP0/COG type, even if substantial more 120pf ... 1.5nF > expensive. I guess the X ceramic will introduce more harmonics than > it will filter out... Thanx for the hint. -- Kovacs Levente Voice: +36705071002 ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
Uwe is spot on. The capacitance vs. voltage of the X7R dielectric is not very good. NP0/COG are usually specified for precision timing and filter applications. NP0/COG also have a much lower temperature coefficient. Andy. On 11 April 2011 15:58, Uwe Bonnes wrote: >> "Kovacs" == Kovacs Levente writes: > > Kovacs> I'm currently designing a power amplifier for the HF (3-30MHz) > Kovacs> radio band. > > Kovacs> I am selecting capacitors for the low pass harmonic filter bank > Kovacs> at the output. My question is what kind of capacitors should I > Kovacs> use? I apply not more then 100V of say 30MHz maximum. > > Kovacs> My best bet is to use X7R capacitors with as much DC voltage > Kovacs> rating as I can get. I don't know if there's any connection > Kovacs> between the DC and AC losses. > > > What value do you need? Try NP0/COG type, even if substantial more > expensive. I guess the X ceramic will introduce more harmonics than it will > filter out... > -- > Uwe Bonnes b...@elektron.ikp.physik.tu-darmstadt.de > > Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt > - Tel. 06151 162516 Fax. 06151 164321 -- > > > ___ > geda-user mailing list > geda-user@moria.seul.org > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user > ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: OFF: capacitors for RF power amplifier
> "Kovacs" == Kovacs Levente writes: Kovacs> I'm currently designing a power amplifier for the HF (3-30MHz) Kovacs> radio band. Kovacs> I am selecting capacitors for the low pass harmonic filter bank Kovacs> at the output. My question is what kind of capacitors should I Kovacs> use? I apply not more then 100V of say 30MHz maximum. Kovacs> My best bet is to use X7R capacitors with as much DC voltage Kovacs> rating as I can get. I don't know if there's any connection Kovacs> between the DC and AC losses. What value do you need? Try NP0/COG type, even if substantial more expensive. I guess the X ceramic will introduce more harmonics than it will filter out... -- Uwe Bonnesb...@elektron.ikp.physik.tu-darmstadt.de Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt - Tel. 06151 162516 Fax. 06151 164321 -- ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
gEDA-user: OFF: capacitors for RF power amplifier
I'm currently designing a power amplifier for the HF (3-30MHz) radio band. I am selecting capacitors for the low pass harmonic filter bank at the output. My question is what kind of capacitors should I use? I apply not more then 100V of say 30MHz maximum. My best bet is to use X7R capacitors with as much DC voltage rating as I can get. I don't know if there's any connection between the DC and AC losses. Thanks, Levente -- Kovacs Levente Voice: +36705071002 ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
