Is this what you expected to happen by adding an inductor? L1 and C1 now form a parallel LC circuit and have a resonance frequency, shown by the sharp peak in the magnitude plot.Īt the resonance frequency, the parallel LC looks like an overall high impedance, and the signal passes through the filter at almost no loss (0dB). The larger capacitance clearly has a lower cutoff frequency (10x larger capacitor means 10x lower bandwidth).Ĭlick Build at the bottom of the window to go back to editing the circuit:ĭrag an inductor from the toolbox and drag to wire it in parallel with C1: This new plot lets us quickly compare the frequency response of the circuit with two different capacitor values for C1, with 1uF in blue and 10uF in orange. Type 'C1.C' in this Parameter box, change Sweep Type to 'Custom', and enter '1u, 10u' in Values: Unsurprisingly, at the -3dB frequency, the linked plot cursors show us that the phase is -45 degrees.Ĭlick to focus the simulation settings window and click the checkmark next to Sweep Parameter: Hover over the magnitude plot to identify the -3 dB point: This is a classic Bode plot, magnitude and phase subplots, with a logarithmically-scaled x-axis. These are the key ingredients of a Bode plot.Ĭlick Run Frequency-Domain Simulation and a plot window appears: The second is PHDEG(V(out)), which asks for the phase in degrees. The first expression is DB(MAG(V(out))), which asks for the magnitude in dB. This tells the simulator to give us more resolution in the frequency domain, at the cost of taking more time to run the simulation.Ĭlick on the node name 'out' and observe that two expressions are added to the simulation settings Outputs list: This tells the simulator that V1 is our driving source, and it should show us the small-signal response relative to changes in that source. Let's have the simulator generate the Bode plot.Ĭlick Simulate at the bottom of the window to open the simulation settings panel, and then click Frequency Domain:Ĭlick the Input field and an autocomplete appears. Great! We've finished drawing an RC low-pass filter. Press N and click to insert a node name label at the top of the capacitor. Press G and click to insert a ground node at the bottom of the voltage source: Flip through the screenshots below to learn how to display a Bode plot in just a few clicks.įrom the toolbox, click and drag a voltage step source, a resistor (press R to rotate horizontal), and a capacitor onto your schematic:ĭrag from component endpoints to connect the circuit with wires: Filters and Frequency Response (Bode Plot)Īmplifiers and filters require thinking in the frequency domain.

Bode plot multisim live