Today let’s continue diving into resistors by exploring the different types based on their construction materials. The material used is important to understand its use cases where you might use one over the other.
Carbon/Ceramic Composition Resistor: These are among the oldest resistor types, made by combining carbon powder and a binding material as a cylindrical core. On top, you have a non-insulating cover for protection. Since the entire body core can conduct electricity, they withstand high-energy pulses. So suitable for surge protection and RF circuits. Since it’s a mixture core, tolerance is not great and can’t be tuned that easily.
Wirewound Resistor: As the name suggests, they are made by tightly winding a resistive metal wire, typically nichrome, around a non-conductive ceramic core. The core provides excellent thermal stability, allowing these resistors to handle high power levels and dissipate heat efficiently. The resistance value depends on the resistivity of the wire and thickness so you can get good precision with it. The drawback is their inherent inductance(basically it’s a coiled wire). So for high freq signals, this resistor is not used widely.. There are variations of this resistor with reduced inductance via certain counter-winding techniques to cancel out the inductance. Overall, it is good for high-power DC applications.
Carbon Film Resistor: These are made by depositing a thin layer(film) of carbon on a ceramic substrate. To adjust the resistance value precisely, a helical or spiral groove is cut into the carbon film using lasers. This process effectively increases the length of the resistive path and allows for fine-tuning of the resistance. They provide better stability, precision and lower noise compared to carbon composition resistors. These are some of the common types seen in the through-hole resistor segment.
There are a few more in the list which we need to go over. Because of the word limit, I will explain them in the next post.
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