Simple resistive load


Sometimes we need to use a resistors that without capacitance or inductance. We always use the carbon resistors. But some working to need the resistor that has also many high power. Which we cannot use the carbon resistor because it has maximum power about 2 watts only.

Normally, performance testing of amplifiers need to apply low resistance load and not affect the frequency. That is pure resistance requirements and The normally power amplifiers have also have high power. (Several hundred watts)

Alternative way is to change the resistor into the wire wound model. This resistor tolerance is very high. Because structure is a wire with a high resistance on the ceramic core. The problem is the inductance hidden inside. Which is caused by winding wire is coiled itself.

Simple resistive load

Figure 1 Simple resistive load

If as the DC circuit this lower inductance, no problem. But for working with high-frequency circuit will result in a lot.

The solution is connects the circuit as Figure 1. The current flow in resistor will opposite and cancel out. However, the total resistance has been reduced from the original. Assuming the value of R, but was divided into two parts. Each section is equal to R / 2 and when the two parts are connected in parallel and be left with impedance R / 4.

This resistor can connects to point out the resistor is (tap). Which currently may be hard to find. But there is another way Using conventional 2-wire resistor with a resistance equal to the parallel instead. But do not forget to consider the resistance forces and the resistance of the circuit is required.


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