Abstract

We attempted to verify the validity of PSPICE simulation and mathematical analysis with Ebers-Moll model by comparing their results for five different circuits which display negative differential resistance (NDR) and multiple operating point (MOP) characteristics. In some cases, we also constructed the actual circuit and used them as references to ascertain the accuracy of the results generated via simulation and numerical analysis. Through these investigations, we have concluded that both SPICE and the Ebers-Moll model are in general accurate at predicting the behavior of circuits with NDR's.

Introduction

Circuits with negative resistances and multiple operating points are useful in applications such as negative resistors and memory cells. However, because of their abnormal behavior, their DC operating points and general behavior are usually hard to predict. In this project, we experimented on five circuits with NDR behaviors, including Schmitt Trigger, Orchard circuit, flip-flop, and two other circuits. We applied theories to predict the circuit behavior, focusing on their operating points and NDR regions, and simulated these circuits with PSPICE and MATLAB in search for their multiple operating points. For the Schmitt Trigger and the Orchard circuit, we implemented the actual design and observed the experimental result through an oscilloscope. The following sections describe the theories applied, the experimental procedure, and the outcomes of our investigation.