EMRFD Message Archive 1143
Message Date From Subject 1143 2007-11-05 11:31:01 Niels A. Moseley BD135 as an RF amplifier
I have recently been exploring the possibilities of constructing an RF
amplifier with current parts. I came across the BD135 transistor which
is still being made by several manufacturers. Some, but not all,
datasheets specify the Ft of the device at around 190 MHz. It has a max.
collector current of around 1.5 amps and a Vceo of 45V.
To me, this looks like a nice QRP device to build a class B push-pull RF
amp with. I designed one in LTSpice which seems to perform well in the
digital world. And this has me worried; why am I not seeing more RF amps
that use this (european) device? Am I missing something here?
I thought I'd ask this list.
73,
Niels PE1OIT
GQRP #11538
ps. EMRFD is the greatest!1144 2007-11-05 12:34:10 Gary Johnson Re: BD135 as an RF amplifier
-Gary, WB9JPS
1145 2007-11-05 15:02:21 Wes Hayward Re: BD135 as an RF amplifier
I was not familiar with the BD135/7/9, so I downloaded the data
sheet. It looks like it would be a great part. I checked DigiKey
and they are available and even cheap here in the US. It looks like
it would work well in the Mark II version of the Universal QRP
Transmitter that was in QST, April 2006, and is also in the 2008 ARRL
Handbook. (Just got a copy in the mail last week!)
I looked at a bunch of those "BD135 QRP Amplifier" listings mentioned
and there were some good things there. In many of the examples,
they were using them as emitter followers. The power was not very
high.1146 2007-11-05 17:16:26 Johan H. Bodin Re: BD135 as an RF amplifier
the BD135 works well in low power HF amplifiers but since it is a "small
transistor in a big package", the hFE (beta) drops rapidly as the peak collector
current exceeds 300mA or so. This may lead to distorsion in a linear amplifier,
I think. You may wish to have a look also at its relatives, BD137 (Vceo = 80V)
and BD139 (Vceo = 100V).
BD131 is a very good european "QRP transistor" for the lower bands (160/80m). I
don't think Philips makes them anymore but it can probably be found in many
Junque boxes. Vcbo = 70V, Ic = 3A, Pd = 15W, Ft = 60MHz. I easily got about 6
watts from a BD131 operating in class E on 1.8MHz with about 100mW (sine wave!)
drive. The transistor had a small heat sink but it wasn't even warm to the
touch. 2 x BD131 worked very well in 5W push-pull 80m linear amp' too.
72
Johan SM6LKM
Niels A. Moseley wrote:
[...]
> I came across the BD135 transistor[...]
1147 2007-11-05 17:16:26 Alan Yates Re: BD135 as an RF amplifier
(and most importantly; I have a bag of them). For a 20 cent transistor
they work pretty well on the lower HF bands, I have an 80 metre DSB rig
that uses two in parallel for the output and one as the driver instead
of a 2N3053.
I've never tried them in Push Pull at RF, I'm sure it would work just
fine, but I'd be interested in seeing your design Niels? (I did make a
small HV inverter with a self-oscillating push-pull pair years ago, I
found them somewhat fragile in this service, I blew up a few from
excessive base drive - but that was my fault.)
Alan VK2ZAY
On Mon, 5 Nov 2007, Gary Johnson wrote:
> To: emrfd@yahoogroups.com
> From: Gary Johns1148 2007-11-05 19:36:11 Allison Parent Re: BD135 as an RF amplifier 1149 2007-11-06 06:40:12 Niels A. Moseley Re: BD135 as an RF amplifier
I googled for BD135 RF amplifier; adding 'QRP' turns up more.
Searching for BD139 is even better! :)
73,
Niels.
> Try Googling: BD135 QRP Amplifier. There are quite a few designs out there.
>
> -Gary, WB9JPS
>
>1150 2007-11-06 06:59:42 Niels A. Moseley Re: BD135 as an RF amplifier
I think the Hfe generally reduces with increased collector current.
The nice thing about the BD135 is that it is a really cheap device.
One could parallel a couple and include emitter ballast resistors to
reduce the transistor Hfe mismatch. Or/and design the amplifier for a
higher Vcc, such as 24V.
When running QRP from home, 24V is no problem. It is less attractive in
the field -- of course.
73,
Niels.
>
>
> Niels,
>
> the BD135 works well in low power HF amplifiers but since it is a "small
> transistor in a big package", the hFE (beta) drops rapidly as the peak
> collector
> current exceeds 300mA or so. This may lead to distorsion in a linear
> amplifier,
> I think. You may wish to have a look also at its relatives, BD137 (Vceo
> = 80V)
> and BD139 (Vceo = 100V).
>
> BD131 is a very good european "QRP transistor" for the lower bands
> (160/80m). I
> don't think Philips makes them anymore but it can probably be found in many
> Junque boxes. Vcbo = 70V, Ic = 3A, Pd = 15W, Ft = 60MHz. I easily got
> about 6
> watts from a BD131 operating in class E on 1.8MHz with about 100mW (sine
> wave!)
> drive. The transistor had a small heat sink but it wasn't even warm to the
> touch. 2 x BD131 worked very well in 5W push-pull 80m linear amp' too.
>
> 72
> Johan SM6LKM
>
> Niels A. Moseley wrote:
> [...]
> > I came across the BD135 transistor
> [...]1151 2007-11-06 07:27:03 Niels A. Moseley Re: BD135 as an RF amplifier
My (LTSpice) design uses them in grounded-emitter configuration. With
12V Vcc I should be able to get 5W peak (2.37W average) out without
coming close to the absolute max. ratings of the transistor. I also use
one BD135 as a class A driver stage.
I'll post the results on the list if and when I build it.
73,
Niels.
> Hi Niels, and group,
>
> I was not familiar with the BD135/7/9, so I downloaded the data
> sheet. It looks like it would be a great part. I checked DigiKey
> and they are available and even cheap here in the US. It looks like
> it would work well in the Mark II version of the Universal QRP
> Transmitter that was in QST, April 2006, and is also in the 2008 ARRL
> Handbook. (Just got a copy in the mail last week!)
>
> I looked at a bunch of those "BD135 QRP Amplifier" listings mentioned
> and there were some good things there. In many of the examples,
> they were using them as emitter followers. The power was not very
> high.1152 2007-11-06 07:41:28 Niels A. Moseley Re: BD135 as an RF amplifier 1157 2007-11-06 14:25:34 Allison Parent Re: BD135 as an RF amplifier 1159 2007-11-07 16:37:06 harold.smith1 Re: BD135 as an RF amplifier
2SC2314. This part is specified as an RF power amplifier, and is used
primarily as a CB driver. I have consistently gotten 2W out of them at
HF (Ft is around 250 MHz). They are also very cheap -- I think I paid
about a quarter apiece for them the last time I stocked up.
Their only downside is that they are hard to find, though they are still
a production part last time I looked. I usually get them from one of
the TV repair suppliers, such as MCM or Match-A-Knob, and those guys
usually have higher minimum orders than some.
Hope this is useful.
de KE6TI, Harold
--- In emrfd@yahoogroups.com, "Allis1160 2007-11-08 07:07:25 Allison Parent Re: BD135 as an RF amplifier