Run an AC sweep
- Open Bode plot, then Run AC sweep. Alternatively select AC frequency sweep in Analysis and press Run.
- Select OUTPUT at C1.+ / R1.2 and REFERENCE at V1.+ / R1.1. Use a sweep from 1 Hz to 100000 Hz.
Check your result
Gain starts near 0 dB, falls near the filter corner and decreases at higher frequencies. Phase moves toward −90°.
If you get stuck: Transfer gain is output divided by the reference signal. Using the output as its own reference produces a flat 0 dB result.
Locate the filter corner
- Hover the gain and phase plots around 159 Hz.
- Expect roughly −3 dB gain and −45° phase. For an automatic limit check, use the tolerance-verification tutorial.
Check your result
Both plots show the expected first-order low-pass behavior near 159 Hz.
If you get stuck: The ideal RC pole is −3.0103 dB. A sampled −3 dB crossing can differ slightly.
Switch back to a time-domain capture
- Set Analysis type to Transient · time domain, select Single capture in the toolbar and press Capture once. Open Spectrum and select the source-positive channel.
- For the default 100 Hz generator, inspect the main peak near 100 Hz. Change the generator to Square, rerun and compare the additional harmonics.
Check your result
The sine is concentrated near its fundamental; a square wave adds higher-frequency content.
If you get stuck: Spectrum uses a Hann window, removes DC and displays up to 256 frequency bins. Capture duration and sampling limit resolution; it is not the same analysis as an AC sweep.