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purpose of very low resistor in power supply filter

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balamani

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Dear Friends,

Please find the attached image. What is the role of 5.1 ohm in the power supply path? I have seen many circuits with very low resistor values ( 0.47 ohm, 20 ohm , 80 ohm etc).

Please explain the significance of this resistor and calculation of this value.

Untitled.jpg
 

it represents the internal resistance of battery...as you are simulating the circuit with ideal components hence for making circuit behavior close to practical,, the low resistance of 5.1 ohm is added in series with the ideal battery component ..
 

it represents the internal resistance of battery...as you are simulating the circuit with ideal components hence for making circuit behavior close to practical,, the low resistance of 5.1 ohm is added in series with the ideal battery component ..
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Did anyone mention circuit simulation? More likely it's a RC filter, intended to remove noise in the supply of a sensitive device, e.g. an analog component.

For a calculation, you need to the device's current consumption and expectable noise frequency spectrum. The filter circuit may be already suggested in the datasheet.
 
Besides filtering the role of such resistor when it has a propper power rating can be a some kind of fuse protection of power supply from short circuit that may happen in the rest of supply chain.
 

Small resistors in series with the filters are often used to improve isolation between the analog and digital circuits in a system if they are both being powered from the same power supply, to keep the digital noise from affecting the analog circuits.
 

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