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Re: gEDA-user: C++ HDL
Stephan Boettcher wrote:
> Joerg <joergsch@xxxxxxxxxxxxxxxxxxxxx> writes:
>
>>>> The topper was a professor at my university who said that soon
>>>> everything will be ICs, that transistors and most of that discrete
>>>> stuff would go away. I burst into laughter in the auditorium, a bit
>>>> embarrassing ...
>>> Well, in case you haven't noticed, it's headed that way. My CCD
>>> measurement chains of 10-20 years ago were full of discrete
>>> transistors. IC's were not up to the job at the power levels required
>>> for a space instrument. Present day versions have no discretes, but
>>> use less power, and are faster and quieter. It's physics: the scaling
>>> laws tell you that in most cases, smaller transistors with shorter
>>> interconnections are better. You can only go so far down this road
>>> with discretes. Still need a big power transistor? Those are mostly
>>> IC's, too: millions of tiny transistors in parallel.
>
> Our charge sensitive preamps for the Radiation Assessment Detector (RAD)
> on the Mars Science Lab mission (launch 2011) use a discrete input FET.
> 17 bit dynamic range are still tough in an integrated circuit, when the
> noise level is supposed to be 1000 electrons, and the largest expected
> signal is 150M electrons. The problem is less with the power, but mass.
> 1cm² board space per preamp is significant weight, if it needs to go to
> Mars. Even more expensive was the paperwork to get that FET (BF862)
> qualified.
>
The BF862 is one fine device. Unfortunately it doesn't come in SC75.
Might be worth looking into some of the Japanese JFETs. There are a few
gems in that group but it depends what you want to do (BW etc.).
Downside is they usually make you buy 10,000 MOQ or so.
AFAIK this mission will launch from Cape Canaveral like usual. Since you
are in Europe, do you know if there's much going on with Ariane from
Kourou? Beside four launches last year I haven't heard much this year.
> Gruß, Stephan
>
> PS: The boards were done with gschem/pcb.
>
Nice.
--
Regards, Joerg
http://www.analogconsultants.com/
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