We have observed that after heating up, mobile phones or desktop or laptop computers start performing slow. why is that?
will the performance increase upon cooling the same device to cryogenic temperature?
Please suggest some articles to go through.
One of the most important environmental parameters is the temperature. It affects the performance of the material from which the devices are made. And thereby the temperature affects the device performance parameters.
The circuits which are the building units of the electronic systems are composed of devices and therefore they are affected by the temperature and so also the system performance.
Therefore one defines what is called the sensitivity of a performance parameter on temperature. One of the important parameter of the digital circuit is their speed of processing which is related to charging and discharging speed of the the MOS transistor gate to source capacitors Cgs in addition to the transit time from the source to drain.
The charging and discharging times is limited by the time constant Ron Cgs. Ron is the on resistance of the transistors. This on resistance increases by the Temperature and thereby the the propagation delay time of the digital circuits increases with temperature.
The transit time = L/vd=L/mu E, where L is the channel length of the transistor , mu is the mobility and E is the electric field.
Normally mu decreases with temperature leading to an increase of the transit time with temperature,
Both effects will lead to reducing the speed of operation with increase temperature.
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The temperature is one of the main parameters that affects the performance of electronic devices. For example, the main unit in the actual electronic devices is the transistor, and this element could be affected by changes in the temperature, causing non-linear distortion (non-linear relationship between the "input" and "output" signals ).
Also the power that a transistor can handle varies in type and application; in some cases they reach very high values and because of the small size of them is difficult to dissipate heat produced during its operation, which can cause loss of energy and affects its response speed for some applications.
Finally, the simple fact that anything that uses energy for an activity result in heat transference; the heat in this case is produced by the disipated power in the resistances of an electronic circuit. Of course, the amount of electricity (voltage and specially current) needed is dependent on the task performed for the phone, desktop or laptop; for example if a CPU operates at a higher clock speed that is intended by its manufactures, it has a faster operating speed, but also requieres more energy to perform the task, this need results in more heat that decrease the speed in time.
Adding to the above posts, the digital circuits are characterized by figure of merit which is the power dissipated Pdis times the propagation delay time Tau. The maximum power dissipated is limited by the allowed operating temperature as the power dissipated raises the temperature of the device. So, the speed of digital circuits ultimately limited by the temperature. As the allowed temperature increases, the power dissipated increases and the delay time decreases increasing the speed of the circuit.
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