How difficult are transistor with an Ft of 5GHz to use? There are
some really cheap ones around these days like the 2sc3356 for
example. I'd like to some to make a regenerative receiver but I worry
that even after careful PCB layout I would still have problems.
Anyway I am starting a new website where I intend to present many
useful circuits. It is located at http://circuitprofile.scienceontheweb.net
At the moment there is only XOR circuit, but that XOR circuit should
be helpful for anyone making a huff and puff stabilized oscillator
circuit.

On Mon, 28 Nov 2011, Lemon Tree wrote:

How difficult are transistor with an Ft of 5GHz to use? There are
some really cheap ones around these days like the 2sc3356 for
example. I'd like to some to make a regenerative receiver but I worry
that even after careful PCB layout I would still have problems.
Anyway I am starting a new website where I intend to present many
useful circuits. It is located at http://circuitprofile.scienceontheweb.net
At the moment there is only XOR circuit, but that XOR circuit should
be helpful for anyone making a huff and puff stabilized oscillator
circuit.

But why?

Cheap really high frequency transistors are great, when you need very high
frequency characteristics.

But there are also plenty of cheap transistors that don't go so high in
frequency that are more than good enough at lower frequencies.

Those "lesser" transistors have to be more available than the really high
frequency transistors.

Take note that a lot of "popular" transistors are that way because they've
been specified in construction articles, which in turn causes the parts
places to carry them, which then also means others specify them in
construction articles.

Michael VE2BVW

On Nov 28, 7:44*am, Lemon Tree wrote:
How difficult are transistor with an Ft of 5GHz to use? *There are
some really cheap ones around these days like the 2sc3356 for
example. *I'd like to some to make a regenerative receiver but I worry
that even after careful PCB layout I would still have problems.
Anyway I am starting a new website where I intend to present many
useful circuits. *It is located athttp://circuitprofile.scienceontheweb..net
At the moment there is only XOR circuit, but that XOR circuit should
be helpful for anyone making a huff and puff stabilized oscillator
circuit.

I hacked a short monopole antenna plus antenna preamp with an NEC
20GHz FET on 1.6mm thick FR4 material, and it worked pretty well. I
needed to have a very linear phase response (20MHz to 2GHz) and it
took some work to get the bypassing right; there was a source resistor
to develop the needed gate bias voltage, and getting it bypassed
correctly kept me busy for a while. One result of the project was
that I became much less afraid to try things like that, though. I
didn't have any stability problems. I used 0402 size parts, mostly
because they fit together better with the transistor than 0603, though
I really don't relish working with things as small as 0402.

I agree with Michael that you should avoid using transistors that have
much higher Ft's than you need, but maybe you're thinking of a 1GHz
regen receiver.

With regard to the parts that places like DigiKey and Mouser and other
authorized distributors stock: I seriously doubt that any homebrew
projects are going to have much effect on what they stock. It's the
parts that are bought for production, by the reel, or at least by
hundreds for some of the more exotic parts, that get their attention.
If you see them with a stock of 10,000 or more of something, you can
bet they didn't get them because they got some orders from random
homebrewers.

Cheers,
Tom

On Mon, 28 Nov 2011, K7ITM wrote:


With regard to the parts that places like DigiKey and Mouser and other
authorized distributors stock: I seriously doubt that any homebrew
projects are going to have much effect on what they stock. It's the
parts that are bought for production, by the reel, or at least by
hundreds for some of the more exotic parts, that get their attention.
If you see them with a stock of 10,000 or more of something, you can
bet they didn't get them because they got some orders from random
homebrewers.

But in the old days, it did matter. When there were local parts stores,
and small mail order places. Why were there all those 2N706s specified
for a long time, until 2N2222s became common? People still specify "1N34"
when what they are really specifying is a germanium small signal diode,
much of the time people didn't really care what the part number was, I
seem to recall ads just saying "germanium diodes".

Even today, there is a relatively small handful of components specified,
albeit a more recent selection.

I have no idea what came first. Did whoever used the 2N706 first look
through databooks and find something "right" and then buy some, or did it
start with going to the parts store and finding what was available? But
as I said, once the parts were in the construction articles, those were
the parts you'd see in the ads, back when the ads were the full line of
what was carried, or a good part of it. Those places didn't carry a full
line, they carried what would sell, so they'd carry what was being
specified in the construction articles.

If you look at the UK or European magazines, you'd see the same small
subset of parts being used, albeit a different set of specific devices.

It still holds true with a place like Dan's Small Parts. He has the
familiar FETs, a dozen or so types of small signal bipolar transistors,
unless he ends up with some overstock of some "exotic" device that's more
or less like the common devices. He doesn't carry endless ICs, so he does
pick to match what is commonly used. It's not a good place for exotic
components or a wide range of components, but for non-digital projects
it's a better place than many, since they carry radio type components like
variable capacitors, so it often avoids orders to multiple places.


The flip side is that in keeping to a small selection of common parts, one
can keep those in stock at home, and be able to throw together a lot of
things on whim. Who doesn't have some 2N3055s and 2N2222s and 2N3906s and
MPF102s?

It was a different era. The hobby suppliers worked as middlemen between
the distributors and the hobbyists. The distributors often didnt' want to
deal with small orders. So new places rose up that would buy in bulk and
sell in small quantities to hobbyists. Since they were small companies in
themselves, they couldn't afford to buy large quantities of lots of parts,
so they picked the popular ones.

I remember about 1974 wanting some "new" ICs, the MC4044P and the MC1648
and the old style parts stores didn't carry things like that yet (and
wouldn't, they'd start disappearing in a few years), so the only way was
to go through a complicated procedure to get them from the local Hamilton
Avnet distributor. And it seemed at the time that they weren't the
general distributors such as Mouser, if you needed some other company's
parts that they weren't a distributor for, you'd have to go to some other
distributor that did carry the line. You'd look in the phone book and
someone would be a distributor for Motorola, another for RCA and so on.

When Active Electronics opened up, it was a big deal because they were
carrying multiple lines, and were sort of willing to deal with the
hobbyist (initially we'd fill out a form, then it would get sent back to
the warehouse to be filled, but slowly they prepackaged components and it
was self serve for the common ones). It was sort of like the old parts
stores, except carrying more leading edge components. But even when a
wider variety of parts was available from places like that, we'd all stick
to more or less the same handful of parts.

Digikey is an example of all this. Started out selling a keyer kit, they
started selling parts and if I'm remembering properly, there was a period
when they listed all or most of their stock in their magazine ads. Then
they grew and grew more, going from a small company catering to hobbyists
with a select number of devices, to being a major source of parts from a
wide range of companies, and really dealing with selling to other
companies, but still having some sort of reasonable policy for the small
time buyer.

Michael VE2BVW

Michael Black wrote:
On Mon, 28 Nov 2011, K7ITM wrote:


With regard to the parts that places like DigiKey and Mouser and other
authorized distributors stock: I seriously doubt that any homebrew
projects are going to have much effect on what they stock. It's the
parts that are bought for production, by the reel, or at least by
hundreds for some of the more exotic parts, that get their attention.
If you see them with a stock of 10,000 or more of something, you can
bet they didn't get them because they got some orders from random
homebrewers.

But in the old days, it did matter. When there were local parts stores,
and small mail order places. Why were there all those 2N706s specified
for a long time, until 2N2222s became common? People still specify "1N34"
when what they are really specifying is a germanium small signal diode,
much of the time people didn't really care what the part number was, I
seem to recall ads just saying "germanium diodes".

In a local homebrewing magazine, they started to use some generic
specifiers for small signal transistors and diodes, and there was a
table in the magazine that listed a number of different types that one
could use.

TUN = Transistor Universal NPN
TUP = Transistor Universal PNP
DUS = Diode Universal Silicium
DUG = Diode Universal Germanium

I think some hobbyists would just go to the store for "5 TUN, 3 DUS"
and get what they needed.

On Nov 28, 9:01*pm, Michael Black wrote:
On Mon, 28 Nov 2011, K7ITM wrote:
With regard to the parts that places like DigiKey and Mouser and other
authorized distributors stock: *I seriously doubt that any homebrew
projects are going to have much effect on what they stock. *It's the
parts that are bought for production, by the reel, or at least by
hundreds for some of the more exotic parts, that get their attention.
If you see them with a stock of 10,000 or more of something, you can
bet they didn't get them because they got some orders from random
homebrewers.

But in the old days, it did matter. *When there were local parts stores,
and small mail order places. *Why were there all those 2N706s specified
for a long time, until 2N2222s became common?
....
Hey, I'm just guessing here, but I'd bet that the 2N706 ("High speed
logic switch," says the data sheet I brought up) was used by the
hundreds of thousands, maybe by the millions, by computer
manufacturers and other industrial/military electronics suppliers back
in the pre-integrated circuit days. That made them inexpensive and
readily available, and on the surplus market. Remember
"PolyPaks" (sp?)? I still have the 30MHz universal counter I built
out of PolyPaks parts, including Nixie tubes. I certainly had no
illusions about me and hobby people like me driving the market for
parts. I remember having a distinct impression at the time that the
hobbyist parts companies bought what they could get their hands on for
very low cost and sold what they could to us geeks. There's a supply-
side reason a lot of those companies were located in the Boston tech
corridor, Silicon Valley, or the L.A. aerospace zone. Yes, certainly
some of them bought stock of things they could move from distributors,
but I still don't see that the hobbyists drove what parts became the
standards.

The people designing ICs these days do it so they can sell large
quantities of them. That means getting them designed into reasonably
high volume products, and that's NOT the hobby or ham market. Heck,
the stuff I design professionally is never sold in high enough volume
to warrant design of any electronics parts 'specially for it, and it's
produced in higher volume than any but the highest volume ham gear--
orders of magnitude more volume than any homebrew projects.

Perhaps we're looking at this from completely different viewpoints.
I'm looking at it from the point of view of a company that makes and
sells, say, semiconductors. From that point of view, you don't ask
how many the hobby market will buy--you find markets that need
millions of parts. If you're successful, you don't mind that a tiny
fraction of those parts end up in hobby projects, but when the main
market dries up, you are unlikely to continue making wafers of that
part just to supply homebrewers.

That's not to say the home experimenter or low-volume industrial user
has no impact on the large (or smaller) semiconductor manufacturer, by
the way. I know that feedback from a ham trying to get low phase
noise, who happened to discover a problem with a particular chip, had
a significant effect on the manufacturer of that chip. I know that my
own feedback to a very large semiconductor manufacturer caused them to
discover a furnace problem and they shut down that line to fix it. I
know that my feedback to the semiconductor product planners that come
by occasionally has some effect on what they decide to do because they
respect that what we do is pretty much cutting-edge, but the ideas
would never see the light of day if they don't see a significant
market for the resulting products (and that market is never going to
be because of things I design, for sure).

Cheers,
Tom

Back in the day.... mid 1960's, I helped out at a service shop in
Goldsboro, NC,
and tried at first to get the shop boss to find a particular transistor or
diode to
complete a repair. He referred me to three cigar boxes. One was for power
transistors, mixed types, another for small signal NPN's, and last for small
signal PNP's. A glass jar held small signal diodes and for larger power
diodes,
I was shown the "back room" where a huge pile of defunct radio, tape player,
TV and
CB radios lie. Help yourself, kid!

Old Chief Lynn, W7LTQ

On 28.11.2011 17:44, Lemon Tree wrote:
How difficult are transistor with an Ft of 5GHz to use? There are
some really cheap ones around these days like the 2sc3356 for
example. I'd like to some to make a regenerative receiver but I worry
that even after careful PCB layout I would still have problems.
Anyway I am starting a new website where I intend to present many
useful circuits. It is located at http://circuitprofile.scienceontheweb.net
At the moment there is only XOR circuit, but that XOR circuit should
be helpful for anyone making a huff and puff stabilized oscillator
circuit.

In most cases high Ft transistors are ok in lower frequency
applications, high Ft means they have current gain which is flat in
frequency and is still some near 1 at Ft.
Oscillations are probably one chance if low frequency design allows
feedback or is not bandwidth limited.

One way out of these is to add extra loss at high frequencies which
lowers gain and lessen probability for oscillations.
Resistor 10..47ohm at collector (base) or tiny ferrite bead has high
impedance at high frequencies but don't affect low frequency
amplification significantly.

In most cases these values need experiments if needed at all, as
instability depends gain used and feedback available.

Gl Kari B

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