EMRFD Message Archive 10650

Message	Date	From	Subject
10650	2014-12-20 19:20:41	bob_ledoux	Transistors for JBOT Amp
Ashar recommends the 2N2218 for the JBOT RF amp.  Is there a list of other transistors that have been successfully used?
10651	2014-12-20 21:06:19	Andy	Re: Transistors for JBOT Amp
Isn't that the same family as the 2N2222? I think there are some differences with power capability, and/or Beta.  The dies are the same but the package isn't. Andy
10652	2014-12-20 21:27:27	Kirk Kleinschmidt	Re: Transistors for JBOT Amp
What we need, I guess, is an Eimac 2N22222222, a transistor about the size of a 3-500Z with 1/8-inch-thick solder tabs :) Actually, until now, I never thought much about why we never see whopper-size transistors, or even if they could be made. That size, they could easily be water-cooled... --Kirk, NT0Z   My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)
10653	2014-12-20 21:38:33	Ashhar Farhan	Re: Transistors for JBOT Amp
well, throw anything at it and see if it sticks. just look at the transistor's Ft and the power dissipation. I'd use anything from BD139s to 2N2219/18/22. You must take the heat away. use a goodish heatsink. - f
10654	2014-12-20 21:53:10	Todd F. Carney / ...	Re: Transistors for JBOT Amp
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10655	2014-12-20 22:40:21	kerrypwr	Re: Transistors for JBOT Amp
I agree with Farhan. I look first at Ft and Ic; those two figures give a good handle on what a transistor can do at RF. I don't discount other parameters of course but Ft & Ic are a good starting point for assessing a transistor for RF service. I've spent many, many hours trawling through transistor data sheets; it's a great learning experience. Kerry VK2TIL.
10657	2014-12-21 09:00:10	Sandeep Lohia	Re: Transistors for JBOT Amp
2N3866 -- Please encourage recycling, reuse or repairing of E-waste. ░7░3░ ░d░e░ ░V░U░3░S░X░T░
10658	2014-12-21 14:00:30	kb1gmx	Re: Transistors for JBOT Amp
2n2222 and the 2n2219 (same for the -A) are both the same die.  The case difference allows the 2219 to handle more power and higher peak currents. Note the pn2222 is lower than the metal case 2n2222. The higher (peak) current is partly due to thicker bond wire used inside.  The hgher power capability is due to the ability of the larger case to transmit heat. Others known to work, I tried them: 2N3553, 2sc1226A  using 6 (3x3) 2n2222A for finals and a single 2n2222A for the driver was happy at 2W output. Heat sink was .5x.25 copper bar for each set of three.  The bar was drilled for a press fit  on the case.   I found the 2N3866 worked but lower gain (its a 28V device).   Others tried: 2sc1906, 2sc2166, 2sc1969, 2sc1970, 2sc1971, 2sc799   All produced more power. Most did in the range of 4-10W for two devices in the output stage.  They also made  good drivers. MOSFets tried:  IRF510, VMP4, VN66, MRF137, RF16HHF. mod if these produced a lot of power once the output transformer was correct.  They required a different bias network. For laughs I tried a MRF136Y (dual device on one header), it was about 15W on 13.8V but easily did 35W using a 24V supply. JOBOT is pretty tolerant but do not try to get more power than the devices and deliver as the circuit tends ot run about 50% efficiency on the final so 4W out means 4W of  heat in the finals.  Like other have said a FT of 250 to 300mhz minimum and Ic in the power range desired. Allison
10659	2014-12-21 14:13:30	kb1gmx	Re: Transistors for JBOT Amp
EIMAC 2n22222222...  that's a 4CX250  with 2000V on the anode and 250ma thats a nice 500W input and 325 out DC to UHF.  Only needs maybe 2W input to do that.  ;) Actually the LDMOS power fets in the MRF1xx and MRFExxxx  are high gain and high power. Good example is the MRF150 a pair of them push pull at 50V will do 300W or more and only need maybe 1-2W of drive.  Most of the good ones want 28 or 50V DC. The little brother of that is the RD16HHF and the smaller brother RF06HHF.  Noth are good to VHF run well at 12V and the digita in the part number give the expected power (16 and 6W respectively). The RD16HHF typiclaly runs about 5$ from reliable sites (RFparts, Kitsandparts are ones I've used). The RD06HHF is cheaper.  Then there is the IRF510.  That has to be the 6146 tube equivalent.  the IRF510 has been  seen in radios doing from 3-5W though a 6M (really VHF)  500W amp (uses 16 of them!).  Its the  closest thing to the HF RF power Swiss army knife.  A pair will easily do 50W at HF using 28V with 2W of drive in a well constructed circuit. Allison
10660	2014-12-21 14:14:20	bobtbobbo	Re: Transistors for JBOT Amp
I haven't tried them in this circuit but I always had good results with 2N4427s in the past. They are a  12 volt device. Bob, K1AO
10661	2014-12-21 17:39:14	farhanbox@gmail.c...	Re: Transistors for JBOT Amp
allison, the irf510s are quite picky about the impedances on both sides. they tend to sing at the slightest provocation like my friend azam. we live with them because they are easy to get. cheap liquor.  - f ------ Original message------
10662	2014-12-21 17:41:50	farhanbox@gmail.c...	Re: Transistors for JBOT Amp
someone must try 2N7000s too ------ Original message------
10663	2014-12-22 14:10:33	kb1gmx	Re: Transistors for JBOT Amp
Funny you say that.  Yes many assume, the input is mosfet, therefore the impedance is  infinite which it is only at DC.  However at RF its a low impedance and reactive at that  and should be matched accordingly.  The second item that's true for it is Ciss thats the  reverse transfer capacitance or simply the effective capacitance between the gate and  drain.  For the IRF510 that's about 20pf, enough to make an oscillator if the input is not  being fed correctly.  What correct, a low impedance source.  How low its a function of  frequency and the 150pf of input capacitance. what does that mean?  at 80M 150pf has a capacitive reactance of  286 ohms, at 10M that's 36ohms!  All power MOSFETs RF or switching  exhibit this.  If your driver is designed for 200ohms on 80m it may work ok but at 10M its not going to do well. I've run it at up to 6M successfully and its gain is still impressive.  That gain will be  troublesome if everything else is not dealt with correctly.  Oddly the device is easier  to tame at higher voltages like 20-30V, and better performing as well.  Like most  T-MOSFET, D-MOSFET the HEX-MOSFET is typically a higher voltage device. I get them to work by treating them as what they are high gain devices  capable of operating at very high frequencies. Things that help the 510 work or sing off tune...  Long gate leads and tracks on  boards are a start of nothing but trouble.   The diver has to be stiff, its going to  deliver some power (ok a half watt) to a stage that is a poor load (reactive  not resistive).   Using the drain lead, cut it off and use the tab, it will also cut  the Drain to Gate capacitance a few pf.  Make the source lead to ground as  short as possible.  Adding some series resistance 1-5 ohms in the gate lead as close as possible to the plastic case helps, ferrite beads there make it worse. Negative feed back helps in some cases (I'v'e used 200 ohms in series with .1uf paralleled with 1uf Drain to Gate) by lowering gain at low frequencies. Oh, the 2N7000 (and Vk10) is worse.  I forgot it on the list, it works well  but it will oscillate at 2M given half a chance.  Its a very high gain device.   If the conditions are met expect 4 of them to do about 1W linear, more  if pushed to class C. The "real" RF devices like RD16HHF and the various MRF, MRFE and  others will behave badly for most of the same reasons.   A BLF177 (improved MRF150) can be loads of fun when provoked.  Tamed a  pair will do more than 300W off a 50V supply all day. Want a working design that took all this into account read WA2EBY and K5OORs work with the HFpacker, or HF using MOSFET. They are not alone. Just some notes. Allison
10664	2014-12-22 15:51:20	iq_rx	Re: Transistors for JBOT Amp
Hi Allison, Farhan and all, Yes, enhancement mode MOSFET capacitance is large, truly interesting, and quite variable as the gate goes from off, to weak inversion, and into strong inversion.  The transitions between the various states are generally not well modeled, particularly in the triode region.  The precise timing of those transitions determines the performance of receivers and transmitters that depend on accurate 90 degree phase shifts between circuit branches. I've had some fun recently building I Q mixers with various devices.  The MOSFETs have outstanding third order dynamic range--when they are off they are nicely off, and when they are on they have wonderfully low Rds--but try to drive a pair of gates with precisely 90 degree phase difference, and those variable capacitors terminating short transmission lines can easily move the zero crossings around by a few electrical degrees. Gate-source capacitance Cgs and gate-drain capacitance Cgd are nearly equal in the triode region (but not in many device models) and both are large, as Allison has noted.  That couples a lot of LO into the RF path.  One interesting result is that some I Q MOSFET mixers that work well at 10 MHz are not particularly attractive at higher frequencies.  The baseband DSP may be perfect, and the 90 degree LO pair from the synthesizer chip accurate to within a fraction of an electrical degree, but the transitions between on and off in the MOSFETS of the I Q mixers may still have large error terms. Learning how to use real devices is at the heart of experimental amateur radio, and very interesting work.  Enjoy the experiments. Best Regards, Rick KK7B
10665	2014-12-22 17:04:15	bob_ledoux	Re: Transistors for JBOT Amp
Here is a presentation by Dan, N7VE, for class E amps using the BS170.  He used these in the Norcal NC2030 transceiver. http://www.norcalqrp.org/files/Class_E_Amplifiers.pdf
10666	2014-12-22 17:04:44	David	Re: Transistors for JBOT Amp
There used to be a fair number of lateral power MOSFETs which should have lower capacitance but except for devices intended for RF applications, they have been replaced with vertical power MOSFETs. On 22 Dec 2014 14:10:31 -0800, you wrote: > what does that mean? at 80M 150pf has a capacitive reactance of > 286 ohms, at 10M that's 36ohms! All power MOSFETs RF or switching > exhibit this. If your driver is designed for 200ohms on 80m it may work ok > but at 10M its not going to do well.
10667	2014-12-22 17:17:24	farhanbox@gmail.c...	Re: Transistors for JBOT Amp
rick. one thing that i did play with was to absorb the input capacitance of the irf510 in a half-wave filter. the amp was touchy but very sensitive! i should played around more but the 40 meter had just opened up for the evening... i wish i had docimented it better. - f ------ Original message------
10668	2014-12-24 12:02:53	kb1gmx	Re: Transistors for JBOT Amp
Rick, having spent a bit of time working with power MOSFETS ( in the sub 5W range) for high effiency HF power conversion I can only say, Amen!  Most spice models are very poor. Look at GAN mosfets.  Some work I've been doing with class D and E say  they are somewhat better. Allison
10669	2014-12-24 14:34:25	kb1gmx	Re: Transistors for JBOT Amp
Interesting work with class E. I did work for the 5W power level using some TI FDC8602 "coolmos" parts  in SOT and with the right driver I was seeing 92%.  It was a way better device  than the BS170.  However the driver sucked down .5W trying to push the gate  hard enough at 20M.  Fairly simple and just works.   But go off on the load and  the device either sees high gate voltage feed back through the drain to gate  capacitance with the high drain peak voltage and dies or if you go the other  way you over current the device and it melts. This was at 12-14V so dropping  to 8V would solve that and still give the power needed with the right output  network. Its not easy to make wide band without giving up some efficiency. Switching amps like that depend on energy storage in the load capacitance or  for class D inductance either way when you store energy like that take care,  the current and voltages can be surprisingly high, even at low power.  That and  driving the mosfet can eat surprising power if not allowed for. The problem with that is for HF when you get over 10mhz the driver is a pain and device capacitance can compromise the design and efficiency. While a high efficiency final sounds good its no fun if your 5W 90% final  needs .5W to drive it, sorta makes the total system efficiency sink real fast. At the 1W power level that CMOS gate is likely doing near its limits  or more at peaks and drawing a fair amount of DC power (likely about .2W). Allison
10670	2014-12-26 08:11:54	jorschei	Re: Transistors for JBOT Amp
Hi All, Look at the Fairchild  RF power Fets type PD85004 and PDT86256 the have a low Gate capacity in the order of 14 pF. Can may be  used for HF to. From Digi Key approx 3 euro PS. Pleas let us Know the results as HF RF amplifier. 73' Joris PE1KTH
10671	2014-12-26 08:44:17	Cecil Bayona	Re: Transistors for JBOT Amp
Are you sure about the second number (PDT86256)? I can't find anything on it from the distributors or Google. At 10:11 AM 12/26/2014, you wrote: > > >Hi All, > > >Look at the Fairchild RF power Fets type PD85004 and PDT86256 the >have a low Gate capacity in the order of 14 pF. Can may be used for HF to. > > From Digi Key approx 3 euro PS. > > >Pleas let us Know the results as HF RF amplifier. > > >73' Joris PE1KTH -- Cecil - k5nwa < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ > Never take life seriously. Nobody gets out alive anyway.
10672	2014-12-26 11:02:12	Graham / KE9H	Re: Transistors for JBOT Amp
I think he meant the Fairchild Semiconductor  FDT86256  Mouser Part #:     512-FDT86256 SOT-89 case. Could be an interesting part, if you can figure out a way to cool it. --- Graham / KE9H ==
10673	2014-12-26 11:18:06	Cecil Bayona	Re: Transistors for JBOT Amp
I have some of those in stock, on my next order will add the PD85004 device to my stock, modest power to 1 GHz, not bad at all. The low input capacity would help with the driver not needing so much power. At 01:02 PM 12/26/2014, you wrote: > > >I think he meant the >Fairchild Semiconductor FDT86256 >Mouser Part #:    512-FDT86256 > >SOT-89 case. > >Could be an interesting part, if you can figure out a way to cool it. > >--- Graham / KE9H > >== > >
10674	2014-12-26 21:59:50	Cecil Bayona	Re: Transistors for JBOT Amp
The tab gets soldered to the PCB with an area big enough to be a heat sink, PCB or Manhattan will work out. At 01:02 PM 12/26/2014, you wrote: > > >I think he meant the >Fairchild Semiconductor FDT86256 >Mouser Part #:    512-FDT86256 > >SOT-89 case. > >Could be an interesting part, if you can figure out a way to cool it. > >--- Graham / KE9H > >== > >
10675	2014-12-27 13:45:18	kb1gmx	Re: Transistors for JBOT Amp
It was mouser 512-fdc08602   screwed up the TI/Fairchild thing. I used a few for class E had upper hf. As to the _he_ got it wrong maybe whoever he is.  I'm an XYL so I got it right. ;) And yes you sill get a headache trying to mount that one.  The SOT89 bits are much bigger. For class E the power dissipation is the small region between on and off.  For JBOT we are talking class B maybe AB1 lin the linear region so getting rid of the heat  is critical. However some of them might make good drivers or earlier stages. Allison
10676	2014-12-27 18:16:42	Cecil Bayona	Re: Transistors for JBOT Amp
Alas you are right again, Mouser doesn't know that part number. I'm curious because I'm always on the lookout for RF power transistor to add to my store. The PD85004 device is interesting because it has such a high frequency range and decent gain. Could the device be the fdc8602 dual MOSFET? At 03:45 PM 12/27/2014, you wrote: > > >It was mouser 512-fdc08602 screwed up the TI/Fairchild thing. >I used a few for class E had upper hf. > >As to the _he_ got it wrong maybe whoever he is. I'm an XYL so I >got it right. ;) > >And yes you sill get a headache trying to mount that one. The SOT89 >bits are much bigger. > >For class E the power dissipation is the small region between on and >off. For JBOT >we are talking class B maybe AB1 lin the linear region so getting >rid of the heat >is critical. > >However some of them might make good drivers or earlier stages. > >Allison -- Cecil - k5nwa < http://thepartsplace.k5nwa.com/ > < http://www.softrockradio.org/ > Never take life seriously. Nobody gets out alive anyway.
10677	2014-12-27 19:20:29	kb1gmx	Re: Transistors for JBOT Amp
So happens it a dual MOSFET.  They work well in parallel. Allison
10678	2014-12-28 12:03:52	in3otd	Re: Transistors for JBOT Amp
I have recently built some small HF amplifiers using the PD85004 and just updated the description on my website http://www.qsl.net/in3otd/ham_radio/PD85004_PP_PA_II/PD85004_PP_PA_II.html . In short, these devices work quite well, but cannot dissipate too much power without having the bias wandering around, due to the high thermal resistance of the package. Still, you can make a good amplifier for SSB... remembers me somewhat of the good old beam power tetrodes designed for the color TV and (ab)used in lot of ham PAs, hi. 73 de Claudio, IN3OTD
10679	2014-12-29 05:29:16	victorkoren	Re: Transistors for JBOT Amp
Claudio, your site with the design and measurements of PA's is very impressive. However I would like to point you to an article that shows why a simple PA output transformer with DC feeding through its center tap is not good for a AB or B class PA. Read this: http://ludens.cl/Electron/mosfetamps/amps.html Its really is an eye opening article. Victor - 4Z4ME
10680	2014-12-29 06:16:54	Claudio Girardi	Re: Transistors for JBOT Amp
Thanks Victor, I read that article a few years ago and, yes, it was really an eye-opener also for me, as I did not think much about how the output transformer winding/core style could affect its actual operation before. What the article points out is that having a *single*, center-tapped turn on a binocular core is the wrong way of building an output transformer, since the two resulting half-turns are actually not magnetically coupled. And unfortunately this is how many high-power PA output transformers are built, with copper tubing used to build the two (uncoupled) half turns. Since then I pay attention to that; the PAs described on my website use a single transformer, but the center tapped winding has always an even number of turns, so every half winding runs thru both holes of the binocular cores; this is a correct way of building the output transformer, as also stated on the original article you linked, "if [...] the primary winding has two turns, with one complete turn on each side of the center tap, then it will work fine too in class AB or class B!". I should probably emphasize this in my description; if I can find some time in the near future I might build an output transformer the wrong way, just to show how bad will be the performances in this case, hi. Thanks and 73 de   Claudio, IN3OTD ----Messaggio originale---- Da: emrfd@yahoogroups.com Data: 29-dic-2014 14.29 A: Ogg: Re: [emrfd] Re: Transistors for JBOT Amp   Claudio, your site with the design and measurements of PA's is very impressive. However I would like to point you to an article that shows why a simple PA output transformer with DC feeding through its center tap is not good for a AB or B class PA. Read this: http://ludens.cl/Electron/mosfetamps/amps.html Its really is an eye opening article. Victor - 4Z4ME
10681	2014-12-29 07:31:54	victorkoren	Re: Transistors for JBOT Amp
You are right Claudio, thanks for the clarification. Victor - 4Z4ME
10682	2014-12-29 08:50:33	jorschei	Re: Transistors for JBOT Amp
Claudio, Excellent PA design width the PD85004 on your site en very helpful data / measurements. I want to build the Push-pull amplifier for 5 watt, it is a  nice PCB design !!! Also think of an 1 watt version experiment and try a modified milled aluminium heatsink thad is clamped on the SOT89 FET and PCB to improve the heat absorption.  Thanks for this helpful  input. 73" Joris  PE1KTH
10683	2014-12-29 09:10:24	Tayloe, Dan (NSN ...	Re: Transistors for JBOT Amp
There are heatsinks that are designed to be soldered to the PCB copper pad the SMT transistor is using.  See Mouser part number 532-573300D00010G.    That might be useful with the 512-FDT86256.  This has 18 ohms of thermal resistance compared to a 1 square inch copper pad thermal resistance of 56 ohms (taken from the ‘86256 data sheet).  It was designed for a larger TO-263, but seems like a useful cooling option for the SOT223-3 package..    That would allow cooling for perhaps 3w of heat.   -          Dan, N7VE
10685	2014-12-30 04:06:33	jorschei	Re: Transistors for JBOT Amp
Dan, This is a good idée of cooling SMD transistors or Fets width an AAVID Surface Mount heat sink. Mouser, No-532-573300D00010G. Also in stock from Digi Key No-HS338TR-ND. When the parts are placed on the board the last action is solder the heat sink over the SMD  Fet. Thad can be done width an hot are tool heat up the heat sink from above until the heatsink pad solder is on temperature. Removing is the opposite way. No mechanical work is necessary. Only have to design the PCB for this heat sink. Shall place some data info in the PE1KTH File. Thanks for the input. 73'  Joris  PE1KTH