The frequency response of a system is yielded from the ratio of the output signal to the input signal the display still must be adapted slightly. After the desired node in the circuit (output) has been selected, the amplitude and the phase are displayed as a function of frequency. After the simulation successfully completes, an empty probe editor automatically opens. Now the actual simulation can be run ( Simulate > Run). In the voltage source parameters under menu item Small Signal AC Analysis, the desired amplitude is specified (1 V here). In addition, for the AC analysis, the input voltage with which the circuit should be stimulated should be defined. The remaining parameter information should be added as required. Under Type of Sweep, the value Decade should be selected. The x-axis in a Bode plot should have a logarithmic scale.

The simulation parameters are also entered here. This requires an AC sweep, which can be found under the AC Analysis tab in the menu Simulate > Edit Simulation Cmd. The circuit will be stimulated with a sine wave. Example of a circuit for a second-order low-pass filter. The input and output nodes were given labels to facilitate the later display of the simulation in the simulation window.įigure 1. Figure 1 shows a second-order low-pass filter. To obtain the frequency response of a circuit, or its Bode plot, using LTspice, it helps to start with a simple circuit example. Thanks to its compatibility with SPICE, LTspice can handle numerous electronic components. In addition, small signal analyses and Monte Carlo simulations can be performed. With this powerful simulation software for analog circuits, signals in the time domain can also be transformed to the frequency domain. The frequency response of an electrical circuit can be simulated with LTspice ®. Simulation of the Frequency Response with LTspice

Further advantages of the logarithmic representation are the larger frequency range of the plot and the identical relative precision over the entire curve. The phase responses can be additively superposed even without the logarithmic scale. If there are several partial transfer functions, the actual multiplication of their amplitude responses is simplified to an addition through the decibel scale. The amplitude response is given in decibels, so it is possible to construct complex Bode plots by superposition of simple subplots. For this, the amplitude response and the phase response are determined from the transfer function of the system and plotted as a graph with the gain and the phase as a function of frequency. This is called the frequency response of the system. For the development of dynamic systems in electrical engineering, control engineering, and even mechatronics, the steady-state response at the output of the system to harmonic excitation (sinusoidal oscillation) at the input often must be known.

Multisim bode plots