Operating range of the devices

electronicsLearner77

Jul 2, 2015
306
I observed for every device there is an operating range specified (ex:IC, individual components and system) by the minimum voltage and the maximum voltage. My understanding as per this specification is that for every device there is a fixed resistance for example R, if the minimum voltage is Vmin and the max voltage is Vmax, the current is Imin = Vmin/R, Imax = Vmax/R. If it exceeds the max value due to dissipation power I^2*R the device burns, am i correct? And for lower limit of current the components inside the device require this much base current to operate?

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,716
My understanding as per this specification is that for every device there is a fixed resistance
Definitely not.
For some devices this may be true, but most any electronic device is much more complex than simply a resistor.
if the minimum voltage is Vmin and the max voltage is Vmax, the current is Imin = Vmin/R, Imax = Vmax/R. If it exceeds the max value due to dissipation power I^2*R the device burns, am i correct?
Partly. For a resistive device your calculation is correct.
But: Min and Max ratings are not purely defined to avoid destruction from overheating due to excessive power. You'll also have to take into account several other factors like for example:
• threshold voltages of semiconductor devices (e.g. when a transistor turn on or off)
• limits to electric fields within a device (e.g. the strength of an electric field between a MOSFET's gate and channel)
• accuracy of the device (some devices work "well" for hobbyist purposes outside the defined min. and ,ax. range, but will probably fail to meet other specs when doing so)
• lifetime of the device (operating e.g. a capacitor above its rated voltage may not immediately destroy the capacitor. It will also not heat up, but the dielectric may be stressed too much so the capacitor may fail early)
• etc. etc.
And for lower limit of current the components inside the device require this much base current to operate?
Not solely. What if the device is a MOS device without bjts? No base current there. Other considerations as above also apply here.

electronicsLearner77

Jul 2, 2015
306
Ok, understood it is a combination of several factors. But one clarification is suppose, if i have a regulator which has the capability of converting a particular input voltage for example the regulator i/p voltage is 18V to 32V and converts into 24V, 5V etc and other voltages as per the specifications of the ICs inside the system. Can i say that the system specification is between 18V and 32V? How do i derive the current range of the system, Is it the sum of currents of the individual ICs?

bertus

Moderator
Nov 8, 2019
3,321
Hello,

It depends on how the voltage regulators are made.
Linear voltage regulators will have a larger loss as switching regulators.
Linear regulators will hardly add noise to the system.
Switching regulators can add noise due to the switching to the system.

Looking at your example with an input range of 18 to 32 Volts with an output voltage of 24 Volts, it must be a switching regulator, likely a sepic or boost-buck regulator.
The attached PDF will show you the possible switching regulators.

Bertus

Attachments

• cd00003910-topologies-for-switch-mode-power-supplies-stmicroelectronics.pdf
233.4 KB · Views: 1

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,716
How do i derive the current range of the system,
From the datasheets of the components and the design specifica of the regulator circuit.

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