[SOLVED] Sense resistor's power dissipation in a constant current source?

[lee321987]

Hello.
I have built a constant current source, and I'm trying to figure out how to calculate the power dissipated by the sense resistor at various currents.

I know how to do this for a voltage source, but i am perplexed as far as a current source....?

The circuit:
+12V-------MOSFET------resistor--------load--------GND

 

[klystron]

I squared times R

 

[lee321987]

Thank you.

 

[lee321987]

Does this equation still work if the current and/or resistance are below zero?

 

[godfreyl]

The resistance of a resistor is never less than zero. The equation works for either direction of current flow.

 

[lee321987]

Oops, i meant: if current or resistance are less than one.

e.g. (0.5A ^2) * 0.3R = 0.075W power dissipation...?

Does it still work?

 

[godfreyl]

e.g. (0.5A ^2) * 0.3R = 0.075W power dissipation...?

Yes, that's right.