Cruise ship stuck in ice

Paul Keinanen <keinanen_at_sci.fi> wrote:
: In order to keep this discussion on topic, why is it so hard to get
: component specifications from semiconductor manufacturers for
: temperatures below 0 C ?

Actually, more and more modern CMOS semiconductors seem to work even
at 4.2K . More so than, say, 15 years ago. My wild guess is that
linewidth reduction combined with higher switching speed requirements
have driven the manufacturers to use heavier doping levels, attempting
to get higher mobility. A side effect is that the carriers no longer
freeze out.

Regards,
Mikko

On Sat, 6 Mar 2010 23:00:26 +0200 (EET), the renowned Okkim Atnarivik
Okkim.Atnarivik_at_twentyfour.fi.invalid> wrote:

Paul Keinanen <keinanen_at_sci.fi> wrote:
: In order to keep this discussion on topic, why is it so hard to get
: component specifications from semiconductor manufacturers for
: temperatures below 0 C ?

Actually, more and more modern CMOS semiconductors seem to work even
at 4.2K . More so than, say, 15 years ago. My wild guess is that
linewidth reduction combined with higher switching speed requirements
have driven the manufacturers to use heavier doping levels, attempting
to get higher mobility. A side effect is that the carriers no longer
freeze out.

Regards,
Mikko


I thought it was primarily bipolar that had problems with 4K
(including such weirdities as Si diodes oscillating. Do you have/would
you be willing to share a list of parts that have been found to work
at liquid He temperatures?


Best regards,
Spehro Pefhany

On Sat, 06 Mar 2010 16:28:07 -0500, Spehro Pefhany <speffSNIP_at_interlogDOTyou.knowwhat> wrote:

On Sat, 6 Mar 2010 23:00:26 +0200 (EET), the renowned Okkim Atnarivik
Okkim.Atnarivik_at_twentyfour.fi.invalid> wrote:

Paul Keinanen <keinanen_at_sci.fi> wrote:
: In order to keep this discussion on topic, why is it so hard to get
: component specifications from semiconductor manufacturers for
: temperatures below 0 C ?

Actually, more and more modern CMOS semiconductors seem to work even
at 4.2K . More so than, say, 15 years ago. My wild guess is that
linewidth reduction combined with higher switching speed requirements
have driven the manufacturers to use heavier doping levels, attempting
to get higher mobility. A side effect is that the carriers no longer
freeze out.

Regards,
Mikko


I thought it was primarily bipolar that had problems with 4K
(including such weirdities as Si diodes oscillating. Do you have/would
you be willing to share a list of parts that have been found to work
at liquid He temperatures?


Best regards,
Spehro Pefhany

I have seen many reports of PCs being super-hotrodded in LN2.

In practice, most problems at low temperature systems are associated
with getting oscillators to oscillate at low temperatures.


Look for categories such as "space and harsh environments", like here:
http://www.linear.com/pc/viewCategory.jsp?navId=H0,C1,C1778,C1503

They also have resistor-set oscillators if you can use those:
http://cds.linear.com/docs/Information%20Card/LTCMP.pdf

What kind of problems do you have to get oscillators started? Russian
truckers sometimes light a little wood fire under the engine to warm it
a bit but I guess that's not an option in your case

On Sat, 06 Mar 2010 11:44:04 -0800, Joerg <invalid_at_invalid.invalid
wrote:

In practice, most problems at low temperature systems are associated
with getting oscillators to oscillate at low temperatures.

Look for categories such as "space and harsh environments", like here:
http://www.linear.com/pc/viewCategory.jsp?navId=H0,C1,C1778,C1503

They also have resistor-set oscillators if you can use those:
http://cds.linear.com/docs/Information%20Card/LTCMP.pdf

What kind of problems do you have to get oscillators started? Russian
truckers sometimes light a little wood fire under the engine to warm it
a bit but I guess that's not an option in your case :-)

An oscillator is simply an amplifier with a frequency selective
feedback path that satisfies the Barkhausen criterion (gain larger
than the feedback path loss).

When an amplifier is powered up with a frequency selective feedback
network, first the wide band thermal noise (about -174 dBm/Hz at room
temperatures) is amplified and the noise after frequency shaping in
the LC network is feed back to the input of the amplifier. After a few
times though the amplifier, the broadband noise has been reduced to a
narrow band single frequency signal, when the amplifier is saturated
by noise.

For a proper startup, the oscillator must start in class A or AB,
while later on, it can drop to class C.

At very low temperatures, if the Barkhausen requirement is not
satisfied, if the gain drops too much at low temperatures, preventing
the oscillation.