Once any of the available ground symbols is added, the simulation will run:Īll simulation schematics MUST have a ground 02 With no ground symbol, the simulation will not run:Īll simulation schematics MUST have a ground 01 This is illustrated in the following two examples: SIMULATION SCHEMATICS THAT DO NOT HAVE A GROUND NODE WILL NOT RUN. The ground node can be placed anywhere in the circuit that is convenient for the purposes of the simulation but it must exist somewhere in that circuit. All voltages probed in the circuit, unless explicitly probed as voltage differences are then measured with respect to that ground node. The following section describes and illustrates some of the most common mistakes, misunderstandings and causes for confusion.Īll simulation circuits MUST have a ground nodeĪ feature of the way simulators work is that they MUST have a ground node (also referred to as the 0 net) somewhere in the circuit.
Learning to use a simulator means thinking more about what the real world really looks like, how it differs from the theoretical world of textbook problems and simple diagrammatic circuit representations and therefore what the results of measurements are likely to be. In cases where there are differences between real and simulated results this may also require a deeper understanding of what is going on in those circuits and what assumptions are being made - often unconsciously - about them. Therefore, it is important to understand exactly what measurements are being made and how the simulation circuit will affect the results. Part of the problem is that a user’s expectations are informed by experience of real world measurements.
The departures from ideal are often different between the two and if these differences between real and simulated components in a circuit are not clearly understood, they can lead to confusion when the results of a even a simple simulation are different from those expected. There are many things that can catch out the newcomer to simulation because neither real world nor most simulator components are ideal. Using a simulator is not quite the same as building a real circuit. DC paths through Voltage and Current Sources.Every point in a simulation schematic MUST have a DC path to ground.All simulation circuits MUST have a power and/or signal source.The ground node MUST NOT have a Voltage Probe attached to it.All simulation circuits MUST have a ground node.