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Re: A high power RF LDMOS transistor
Clifford Heath wrote...
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 Yes, very interesting designs with the MRFE6VP61K25HR5.
 The "50V" device labels mislead me.  While I read 50V,
 they actually said Vdd = 50V, and the part had a 125V
 maximum spec. OK.   The drains would nominally swing
 to 100V max in the designs.  

 Misreading the MRF1K50H 50V spec as the maximum implies
 20V supplies, etc.  Hah, a 135V datasheet maximum is
 good, but the $230 to $270 prices slow one down a bit.  
 There are more affordable RF power transistors in this
 class, like the 25W 133V MRFE6VS25NR1 driver for $26,
 and older parts like the 120V 30W MRF148 sell for $38.

 Some of us use these MOSFETs as fast high-current 25
 or 50-ohm DC switches, rather than as RF amplifiers.
 Of course, we'd like to see higher voltage ratings.
 I've been working with 1200V low-capacitance SiC
 power MOSFETs, 1.2kV is more like it!  For example,
 whereas the MRFE6VS25NR1 shows Coss = 15pF at 50V
 on its plot, a Cree C2M0280120D shows 35pF at 200V.
 OK, that's certainly not exactly an RF transistor!


--  
 Thanks,
    - Win

Re: A high power RF LDMOS transistor
On 28/08/16 22:46, Winfield Hill wrote:
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Not if you're a hobbyist with access to dozens of retired
analog TV modules :) The BLF278 isn't quite as grunty, but
still...

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How is a 25W or 30W transistor in the same class as a 1250W one?

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How fast? I recall you reproducing McEwan's claim of
a 1kV step in 1ns, after I brought that up here years
ago, and the possibility was debated. I forget what you
used then.

Am I right in saying that the 1.6 + j5.0 input impedance
in that 2m amp implies an input capacitance around 680pF
(5 ohms at 146MHz)? Or is that the differential (series)
capacitance between the 2 gates.

I'd like to learn more about how these transmission-line
transformers are designed... any pointers? or any discussion?

Clifford Heath

Re: A high power RF LDMOS transistor
On Mon, 29 Aug 2016 10:35:54 +1000, Clifford Heath wrote:

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Loads of stuff on the subject in these yearly manuals:

http://tinyurl.com/jp7cyqh

I prefer the older editions from the a few decades ago (pre-SMT) but YMMV.

Re: A high power RF LDMOS transistor
On Fri, 26 Aug 2016 22:25:21 -0400, Michael A. Terrell wrote:

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w-cw-over-1.8-500-mhz-50-v-wideband-rf-power-ldmos-transistor:MRF1K50H>

Wow! That *is* impressive. As will be Trump's landslide victory come  
November. >:->

Re: A high power RF LDMOS transistor
On Sunday, August 28, 2016 at 12:21:51 AM UTC+10, Cursitor Doom wrote:
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As will the clouds of pigs flying overhead, each with its own orange toupee.

--  
Bill Sloman, Sydney

Re: A high power RF LDMOS transistor
Cursitor Doom wrote:
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The best possible outcome is that Hillary is elected and then falls over  
again within two months, but doesn't get up this time.

Of course it would be better if Mike Pence became president but Trump is  
as unlikely to drop dead soon as he is to get elected.




Re: A high power RF LDMOS transistor
On Sat, 27 Aug 2016 19:50:48 -0400, "Tom Del Rosso"

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I was thinking the same thing the other day.
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But he will have a target on his back.  Pence isn't good life
insurance.


Re: A high power RF LDMOS transistor
On 28/08/16 00:53, krw wrote:
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Unlike Dan Quayle. Although Quayle was more likely
anti-impeachment insurance.


Re: A high power RF LDMOS transistor
On Sun, 28 Aug 2016 01:04:37 +0100, Tom Gardner

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How about Spiro Agnew?  Except that even he wasn't enough impeachment
insurance, so he had to go first.

Probably closer to LBJ, as far as assassination insurance goes.
...except they didn't count on a loose nut.



Re: A high power RF LDMOS transistor
On 28/08/16 01:59, krw wrote:
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Not really in either case. You state the reason for Spiro
the Gyro.

LBJ was intelligent and effective, cf Quayle.


Re: A high power RF LDMOS transistor
On Sun, 28 Aug 2016 07:58:42 +0100, Tom Gardner

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Intelligent, effective, and widely despised.  He delivered the black
vote for at least two generations, though.  Even if he did screw over
the blacks, and the cities, at the same time.


Re: A high power RF LDMOS transistor
On 28/08/16 23:16, krw wrote:
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Haven't all recent presidents been "widely despised"? Soft money
and pressure groups are a scourge.

Would you prefer to have a stupid ineffective president? Do you that
would be better for the US?

Re: A high power RF LDMOS transistor
On Mon, 29 Aug 2016 00:16:05 +0100, Tom Gardner

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By other politicians?  No, not really.

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In the case of LBJ (or Jimmy Carter or Barak Obama), you bet!

Re: A high power RF LDMOS transistor
On 29/08/16 02:14, krw wrote:
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Colour me surprised.


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Well, you could always join 3rd world countries and elect
a second-rate movie actor whose training is to be told what
to do by the puppetmasters behind the cameras.



Re: A high power RF LDMOS transistor
On Mon, 29 Aug 2016 11:04:40 +0100, Tom Gardner

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Works for me (though I didn't vote for him the first time around).

Re: A high power RF LDMOS transistor
On Sat, 27 Aug 2016 19:50:48 -0400, Tom Del Rosso wrote:

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Pence is Establishment. If they can't control Trump - as appears - he'll  
get whacked just like JFK and Pence will take over.

Re: A high power RF LDMOS transistor
On Friday, August 26, 2016 at 10:25:30 PM UTC-4, Michael Terrell wrote:
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NXP bought out the Freescale LDMOS line and then sold their line to a chinese company called Ampleon.  Freescale makes great LDMOS parts and now NXP owns them.  

Re: A high power RF LDMOS transistor
On Fri, 26 Aug 2016 22:25:21 -0400, "Michael A. Terrell"

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LDMOS is impressive - look at that transconductance! - but
capacitances are high and need to be tuned out, so they are not very
"wideband." That part has a gate capacitance of 664 pF and reverse
transfer 3.5.

The real killers are GaN fets, which have similar DC specs but tiny
capacitances.  


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: A high power RF LDMOS transistor
On 08/30/2016 01:26 PM, John Larkin wrote:
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Wonder if they'd make good bootstraps.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: A high power RF LDMOS transistor
On Tue, 30 Aug 2016 13:54:03 -0400, Phil Hobbs

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GaN fets tend to be power-ish parts, although some GaN MMICS are
starting to appear. Their Gm is high and Cdg is low. They behave very
well. But I'd expect, wild guess, more LF noise than a jfet.

Have you tried PHEMTS, like the Avago ATF series? Those might be
better for smaller apps.



--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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