From: Winfield Hill
Subject: Re: Q. medium-power RF transistor
Date: 10 Nov 2002 04:32:58 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.10
> Helmut Sennewald schrieb ...
>> Winfield Hill schrieb ...
>>> email@example.com (carltons) wrote...
>>>> Helmut Sennewald HelmutSennewald@t-online.de wrote:
>>>>> Winfield Hill schrieb ...
>>>>>> I'm thinking about making 20 to 30V pulses with a
>>>>>> 1ns max risetime into a 50-ohm line...
>>>>>> What's a good low-capacitance transistor to use with
>>>>>> say Vceo 30V, 500mA capable (h_fe >10 at 500mA) and
>>>>>> with f_T of at least say 1GHz at Ic 200mA, Vce 15V?
>>>>> Hello Win,
>>>>> I would try four cascodes in parallel with BFG135 transistors.
>>>>> http://www.semiconductors.philips.com/pip/BFG135.html ...
>>> That's a nice transistor, reasonable beta at 100mA, with just
>>> over 3pF of Ccb+Coe capacitance. I could parallel four with
>>> a 50-ohm pullup to 25V (each in common-base mode, Vcbo = 25V),
>>> and still have RC under 1ns. And it looks easy to get.
>>> But I wonder, where have all the medium-current 25+ volt RF
>>> transistors gone? All the likely parts I have examined are
>>> discontinued. For example, an ON Semi MRF3010 or MRF134 RF
>>> MOSFET (65V, 1A, Coss + Crss < 12pF) would have been nice a
>>> few years ago. What's the ticket now?
>> Hello Win,
>> I have looked in my archive about my older contributions and
>> found links to the RF-Power Mosfet. Hopefully I could help you.
>> Best Regards
>> ---- Original text follows ----------------------------------
>> NG: sci.electronics.cad
>> Date: 20.3.2002
>> Thread: Re: high speed power mosfet models
>> Hello Steve,
>> Take a first look here http://www.polyfet.com/xref.htm as Mohi
>> already recommended, and choose the replacement part. Then go
>> to their part and take the appropriate SPICE model from Polyfet.
PolyFET looks like a great source for legacy RF power transistors.
Maybe some powerful new ones as well.
>> Some general info from ST:
A nice little article.
> I forgot one of my newer links to power mosfets:
Yep, I had discovered that M/A-Com seems to now have Motorola's
former extensive line of RF power MOS transistors: data sheets,
application notes and all. Picking and choosing which parts to
keep, I suppose. But they have the MRF134 that looked promising,
as does PolyFET for that matter.
I'll also examine M/A-Com's newer offerings. Thanks greatly
Helmut, you have given me some good leads and answers! I'll
report back here in a few weeks as to my success. :-)