铜箔允许通过最大电流DN-71 Design Note Using Copper PCB Etch for Low Value Resistance by Larry Spaziani INTRODUCTION Current sensing in power supplies and motor controls demand the use of a very low value resistor. Each application varies in need for resistance value, power rating, size, form factor, inductance, temperature coefficient and accuracy. To meet some of these applications, the copper of a printed circuit board (PCB) can be utilized, but has some distinct limitations. This design note provides design equations and recommendations for designing resistors with PCB copper. DESIGN OF A COPPER PCB RESISTOR The resistance, as a function of temperature, for a piece of metal, is given by the equation: R(T) = These constants apply to the standard commercially annealed copper used in PCB technology. The resi……