![]() ic | node id or number = initial voltage ic being set then the capacitor would not charge because the default simulation behaves this way. By default LTSpice assumes all captivators have aįull charge. The initial conditions command ".ic", is used to define the voltage of a particular node when a simulation is run. ic This command sets the initial conditions of a node. This time constant to show the state after 10RC constants, which will be shown on the graph, however, first we need to So with values chosen 5RC = 25ms Now I've used double After 5 time constants it reaches 99% of its charge. Value of the resistor and capacitor and this gives you one time constant, or the time it takes for a capacitor to reach 63% Well a capacitor has a time constant of RC, you multiply the Paragraph I said you need to know something about the signal. How did we arrive at the figure 50 milliseconds? Remember in the first Is performed, and when sufficient points have been calculated, a graph can be drawn. For every point on the graph a calculation Value itself, but entering a value can speed up calculations. In many cases LTSpice is clever enough to predict this The maximum timestep option has been left out. The simulation command can be placed on the schematic. ![]() Click on the transient tab, then enter a stop time of 50m and a start time of 0. You will see the followingĭialogue box (shown left). To enter the transient command you can go simulation menu and click on edit simulation command. tran start time | stop time | max timestep Or to speed up long simulations, you can manually enter a value. The maximum time step can be calculated bt LTSpice itself, Time constants, the start time, stop time and maximum time step. Like the measure command, the transient command starts with a period, "." then the work "tran" followed by a series of In order to view this curve you need to know two commands, the transient command and the initial condition command.Īn explanation of these two commands now follows. When power is applied to a capacitor the voltage will rise exponentially and this is a good curve to view in LTSpice. See the previous page onĭrawing the Schematic if you have trouble. In this circuit the DC voltage source is set to 10 Vdc. Like the resistor,capacitor, inductor and ground symbol can be selected from the top menu line. The F2 key will give access to all the components in LTSpice, frequently used parts Either from theĮdit menu, or by pressing F2. Start LTspice and select New Schematic from the File Menu. You must know something about the signal to set-up the correct parameters for a transientĪnalysis. This mode of analysis is very similar to viewingĪ waveform on an oscilloscope. Transient analysis allows you to view signals in the time domain. Please also read my sitesĬalculating Phase Difference using Cursor This advice does not replace the information given by Linear Presented here is my own work and not from Linear Technology.
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