blocco a spirale
- Joined Jun 18, 2008
- 1,546
If you want the signal to be 10 times bigger, use a 1 Ohm I-sense resistor. Apart from the worst case 0.3V drop (which can be overcome) it's a whole lot better and less hassle than adding an op-amp.
While changing Rsense to 1 Ohm would work, the OP would dissipate 10x the power across the 1 Ohm as the 0.1 Ohm resistor. The power dissipation will require going to a much higher rated power resistor; non-inductive versions of these can be difficult for a hobbyiest to find. Ohmite does make non-inductive wire wound power resistors; I've found them on Mouser and Digikey. However, at 0.3v/1 Ohm, he could still use a 1/2W carbon film resistor. It kind of depends on how the OP is powering their circuit, and what kind of efficiency they are expecting out of it.If you want the signal to be 10 times bigger, use a 1 Ohm I-sense resistor. Apart from the worst case 0.3V drop (which can be overcome) it's a whole lot better and less hassle than adding an op-amp.
I'm afraid I don't understand any of this talk of high-power wire-wound resistors as a 1 Ohm resistor only has to dissipate 0.09W worst-case which just about any old resistor will manage. 1% O.6W 1R metal films are available just about everywhere.While changing Rsense to 1 Ohm would work, the OP would dissipate 10x the power across the 1 Ohm as the 0.1 Ohm resistor. The power dissipation will require going to a much higher rated power resistor; non-inductive versions of these can be difficult for a hobbyiest to find. Ohmite does make non-inductive wire wound power resistors; I've found them on Mouser and Digikey. However, at 0.3v/1 Ohm, he could still use a 1/2W carbon film resistor. It kind of depends on how the OP is powering their circuit, and what kind of efficiency they are expecting out of it.
For the OP's benefit - you would not want to use a typical wire-wound power resistor in your circuit, as when the current through the resistor changes significantly there will be an inductive "kick" or voltage spike across the inductive resistor. This will cause the output to fluctuate wildly.