Hi all,

I have a PCB with SMD components. I noticed that there are many resistors is parallel. For instance, two 300ohms SMD resistors are used as a current limiter for an LED. Why is that? Why they did not use a single resistor?

Thanks in advance.

 

You mean voltage divider connection?

 

hi Dri,
Its possible the dissipation in a single SMT of that case size, does not have the required heat dissipation, so two, of double the resistance value are connected in parallel.?

 

If they are connected in series then they probably had lots of 300 Ohm R but didn't have any 600 Ohm R so they connected them in series to save on budget?

 

Thanks for the replies. Ericgibbs answer makes sense for the LED current limiter resistor since this PCB is powered using 12V without a regulator.
But I also noticed the same technique used with buttons. This PCB has surface mount buttons which are resistance coded (for instance when button A is pressed it outputs 300ohms... when button B is pressed it outputs 600ohms etc.). In this case power is not an issue since it will most probably be connected to a voltage divider and to an ADC. So in this case why are they connected in parallel? could it be budget wise or to increase efficiency when placing the SMD components?