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# Low temperature electronics
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This wiki page is dedicated to electronics that has to be used at
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extremely low temperatures.
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-----
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## Training
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- [Extreme-temperature electronics -
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ETE](http://www.extremetemperatureelectronics.com/), Randall
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Kirschman,
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Ph.D.
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- [Tutorial](http://www.extremetemperatureelectronics.com/tutorial1.html)
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-----
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## Practical tips
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### Tips from Nikolai Beev/CERN
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I've built cryogenic amplifiers working in liquid helium, and also SQUID
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readout setups operating at even lower cryogenic temperatures in
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dilution refrigerators (down to \<100 mK).
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So here's a quick list of what works and what doesn't:
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1. Bipolar Si transistors and diodes don't work.
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2. Shottky diodes usually work, their forward voltage drop increases
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3. LEDs work, also with increased Vf and brightness
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4. Most signal MOSFETs work. Many CMOS ICs work as well, including
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digital logic and a few op amps
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5. Some SiGe transistors work and even become better (lower noise,
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higher gain and bandwidth). But they are difficult to tame and prone
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to oscillations in the GHz frequencies.
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6. Small signal relays usually work. I've used plenty of latching Omron
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relays for switching things in the cold.
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7. Thin film resistors with tempco of 25 ppm/K or lower work fine.
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Thick-film resistors made of RuO2 go up in resistance and can be
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used for thermometry.
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8. From the ceramic capacitors, only NP0 don't freeze out. Forget about
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high-value X7R and the kind.
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9. Plastic capacitors usually work fine. Panasonic ECPU are a good SMD
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series with PPS dielectric - others should be fine too (PET or PP).
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10. Forget about electrolytic capacitors. Only Niobium ones work
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somehow, but poorly.
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11. Most ferromagnetic materials freeze out. Some Vitrovac tape-wound
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cores don't. Interestingly, circulators work too, though no one
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knows exactly what kind of ferrite material they use (-:
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### Tips from Stephane Franck Rey / CERN
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I've used some analog multiplexers TC74HC4051 down to 1.7K without any
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problem. However the switch resistance was much below the min value from
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the datasheet of course, which was a benefit for my application.
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The multiplexers had X7R bypass capacitors, PCB was standard FR4,
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soldering made with a small reflow oven in my lab. Everything went
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perfectly. However, do not expect to guaranty reliability without doing
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a proper qualification. A single board which survives may be just a bit
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of luck...
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-----
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31 January 2017
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