Negative Resistance

Summary

Hello! The blog you’re trying to reach is currently unavailable. I am Skippy, your friendly blog assistant. How can I help you today?> quit I’m sorry. This function is currently available only to Skippy Premium and Premium+ subscribers. Would you like to talk about ✨ negative resistance instead?> nope I’m sorry. This function is currently available only to Skippy Premium and Premium+ subscribers.Welcome. Welcome again. If you tinker with analog electronics, you might have heard that some circuits can exhibit negative resistance. This is usually followed by a current-to-voltage plot featuring some sort of a kinked curve and an assertion that this property might help the circuit designer in some way.But what does it mean, exactly? The concept of negative resistance is interesting, counterintuitive, and explained on Wikipedia in a rather rambling way. If you’re up for it, I think we can do better than that.The article assumes familiarity with voltage, current, and the behavior of operational amplifiers. If you need a refresher, start with this primer, then read up about transistors here and signal amplification here.As a quick recap, resistance (R) can be understood as the opposition to the flow of steady current through some portion of the circuit. The quantity describes the relationship between the applied electromotive force — that’s voltage — and the amount of charge moving per second (that’s current).In contrast to some other phenomena in electronic circuits, resistance is not inherently dependent on time or signal frequency. If you know the voltage (V) applied to a purely-resistive component, the current (I) flowing at that exact moment is simply:In resistors, the parameter remains constant across a wide range of operating conditions. This means that if we plot I in relation to V, we get a straight line that crosses through the center of the coordinate system. The slope of the line depends only on the component’s resistance:Resistor I = V/R plots for R = 0.2, 1, ...