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.Andy10652 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, NT0ZMy 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.- f10654 2014-12-20 21:53:10 Todd F. Carney / ... Re: Transistors for JBOT Amp 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 2219to 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 capabilityis due to the ability of the larger case to transmit heat.Others known to work, I tried them:2N3553, 2sc1226Ausing 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 fiton 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 madegood drivers.MOSFets tried:IRF510, VMP4, VN66, MRF137, RF16HHF. mod if these produced a lot of power oncethe 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 buteasily did 35W using a 24V supply.JOBOT is pretty tolerant but do not try to get more power than the devices and deliveras the circuit tends ot run about 50% efficiency on the final so 4W out means 4W ofheat in the finals.Like other have said a FT of 250 to 300mhz minimum and Ic in the power range desired.Allison10659 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 inputand 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 needmaybe 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 VHFrun 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 beenseen in radios doing from 3-5W though a 6M (really VHF) 500W amp (uses 16 of them!). Its theclosest thing to the HF RF power Swiss army knife. A pair will easily do 50W at HF using 28Vwith 2W of drive in a well constructed circuit.Allison10660 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, K1AO10661 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
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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 isinfinite which it is only at DC. However at RF its a low impedance and reactive at thatand should be matched accordingly. The second item that's true for it is Ciss thats thereverse transfer capacitance or simply the effective capacitance between the gate anddrain. For the IRF510 that's about 20pf, enough to make an oscillator if the input is notbeing fed correctly. What correct, a low impedance source. How low its a function offrequency and the 150pf of input capacitance.what does that mean? at 80M 150pf has a capacitive reactance of286 ohms, at 10M that's 36ohms! All power MOSFETs RF or switchingexhibit this. If your driver is designed for 200ohms on 80m it may work okbut 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 betroublesome if everything else is not dealt with correctly. Oddly the device is easierto tame at higher voltages like 20-30V, and better performing as well. Like mostT-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 devicescapable of operating at very high frequencies.Things that help the 510 work or sing off tune... Long gate leads and tracks onboards are a start of nothing but trouble. The diver has to be stiff, its going todeliver some power (ok a half watt) to a stage that is a poor load (reactivenot resistive). Using the drain lead, cut it off and use the tab, it will also cutthe Drain to Gate capacitance a few pf. Make the source lead to ground asshort as possible. Adding some series resistance 1-5 ohms in the gate leadas 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 wellbut 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, moreif pushed to class C.The "real" RF devices like RD16HHF and the various MRF, MRFE andothers will behave badly for most of the same reasons. A BLF177(improved MRF150) can be loads of fun when provoked. Tamed apair will do more than 300W off a 50V supply all day.Want a working design that took all this into account read WA2EBYand K5OORs work with the HFpacker, or HF using MOSFET.They are not alone.Just some notes.Allison10664 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 KK7B10665 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.pdf10666 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
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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 effiencyHF 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 saythey are somewhat better.Allison10669 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" partsin SOT and with the right driver I was seeing 92%. It was a way better devicethan the BS170. However the driver sucked down .5W trying to push the gatehard enough at 20M. Fairly simple and just works. But go off on the load andthe device either sees high gate voltage feed back through the drain to gatecapacitance with the high drain peak voltage and dies or if you go the otherway you over current the device and it melts. This was at 12-14V so droppingto 8V would solve that and still give the power needed with the right outputnetwork.Its not easy to make wide band without giving up some efficiency.Switching amps like that depend on energy storage in the load capacitance orfor 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 anddriving 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 apain and device capacitance can compromise the design and efficiency.While a high efficiency final sounds good its no fun if your 5W 90% finalneeds .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 moreat peaks and drawing a fair amount of DC power (likely about .2W).Allison10670 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 --- Graham / KE9HCould be an interesting part, if you can figure out a way to cool it.I think he meant theSOT-89 case.
Fairchild Semiconductor FDT86256
Mouser Part #: 512-FDT86256
==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 FDT86256Â
>Mouser Part #: Â Â Â 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 FDT86256Â
>Mouser Part #: Â Â Â 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 JBOTwe are talking class B maybe AB1 lin the linear region so getting rid of the heatis critical.However some of them might make good drivers or earlier stages.Allison10676 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.Allison10678 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: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: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 - 4Z4ME10682 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 PE1KTH10683 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