Re: gEDA-user: C++ HDL

[Stephan Boettcher <boettcher@xxxxxxxxxxxxxxxxxx>]

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.

Gruß, Stephan

PS: The boards were done with gschem/pcb.

-- 
Stephan Böttcher                     FAX: +49-431-880-3968
Extraterrestrische Physik            Tel: +49-431-880-2508
I.f.Exp.u.Angew.Physik               mailto:boettcher@xxxxxxxxxxxxxxxxxx
Leibnizstr. 11, 24118 Kiel, Germany


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