LOW TEMPERATURE ELECTRONICS - FOR SPACE
What is the temperature on other planets ? -150˚C at the orbit of Jupiter, -230˚C at the orbit of Pluto and below -55˚C to -65˚C at Mon, Mars and asteroids. At such low temperatures, conventional temperature electronics is not of help.
So researchers are pioneering a technology called 'low temperature electronics' or 'cryoelectronics'. Cryoelectronic materials with high carrier mobility and reliability might provide a better solution for circuits to be used in low temperatures.
WHAT IS CRYOELECTRONICS ?
'Cryo' is derived from Greek word which means 'Kryo' which means 'icy cold' or 'frost'/ Cryogenic temperature ranges from -150˚C to -273˚C. Cryoelectronics deals with production of low temperature electronic devices and utilisation of low-temperature phenomenon. Examples of these evices are CMOS diodes and FETs .
WHY TRADITIONAL ELECTRONICS CANNOT BE USED IN SPACE ?
Electronics plays an important role in spacecrafts. It is used in sensors, cameras, wireless data transmission, etc. Conventional temperature electronics work between -55˚C/-65˚C and 125˚C. Low temperature electronics, on other hand, works at temperature ranging from -150˚C to -273˚C.
In military and scientific aircraft, many sensors such as X-ray detectors are used for astronomical observation or surveillance. These must operate at low temperature. Cosmic background explorer, infra red telescope in space and infra red space observatory are some of the devices which makes use of cryoelectronics-based electronic components.
|Testing equipment for low temperature electronics|
Conventional temperature electronics circuits require a thermal source for low temperature applications. In many situations, such techniques are undesirable or impractical. Passive techniques have limited lifespans. Active technologies, on the other hand require additional power and sub-systems. This makes electronic circuits bulky, heavy and complex.
CRYOELECTRONICS IN SPACE TECHNOLOGY
NASA in using components such as semiconductors switching devices, magnetic capacitors, digital-to-analog and analog-to-digital convertors, DC-AC convertors, operational amplifiers, oscillators and power conversion and conditioning circuits based on cryoelectronics. Cryoelectronics is also used in driver circuitry of motors or actuators. Commercial high speed Pulse Width Modulation (PWM) chips have been characterised in terms of their performance in the range of 25˚C to -196˚C. Silicon-on-Insulator (SOI) can be used to make MOS devices with gates as small as 40 nm.
Advantages of cryoelectronics for space technology are increased circuit sped, low power dissipation, fast switching, high semiconductor and metal thermal conductivity, reduction in thermally induced failures of components and devices, increased integration density primarily because of reduced operating supply voltages and improved digital and analog circuit performance( in terms of speed, switching, noise margin and gain bandwidth) .
Disadvantages include novel fabrication technique required, low carrier mobility, high cost of circuit and high volume.
Cryoelectronics find application in outer space satellite eg in sensors for flow, temperature and pressure measurement; detectors of cosmic radiation such as infra red and ultra violet detectors; nuclear astronomy instruments; medical instruments; dynamic random access memories; highend computers and organic electronics