Resistor is a two terminal component. It is mostly used for
current limiting, Potential divider, Pull up and Pull down purposes.
Resistor is made up of insulating material such as carbon to
restrict the flow of electrons, while doing this it dissipates heat. The
resistor will blow up, if the heat dissipation of a resistor is greater than
the value it is rated for.
How to select a resistor?
The below main parameters will be considered while selecting
a resistor,
1. Resistor value
2. Power Rating
3. Package (SMD or Through hole)
Resistor Value:
A resistor is chosen based on the
voltage drop across it and the current it should allow.
If the required voltage drop
between the two nodes is 2V and the current in that loop is 4mA then the
resistor to be placed between those two nodes is 0.5K
R=V/I=2V/4mA=0.5K
Power Rating of a resistor:
Power rating of a resistor is based on the current passing
through it. Suppose if a resistor with the value of 10K needs to allow 10mA
current safely without over heating, then the power rating of that resistor
should be 1W.
P=I2R=10mA*10mA*10K=1W
Package:
Package of a resistor depends upon the board size, frequency
of operation, soldering and power rating requirement.
SMD is suitable for small size board, higher frequency of
operation, automated machine soldering.
Through hole is suitable for bigger size board, board with
lower frequency of operation such as power supply boards and for hand/wave
soldering. The higher power rating resistors are available mostly in through
hole package only.
Some of the Leading Manufactures:
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