Capacitors not removing DC component after new update.

Question

Hi, I wasn't sure where to post this. If I shouldn't post here, please let me know where could I do so. I wanted to let you know of a current bug in the latest LTSpice version. Now, capacitors wont filter DC components unless there's something connected after the capacitor and directed to ground. This wasn't happening as of v24.0.8. After updating, this issue started to appear.

VilemK · Accepted Answer

You're right to ask &mdash; this is an important detail that&rsquo;s easy to overlook. 
 If you connect an oscilloscope probe to Vo in a real circuit, then yes, the signal will appear centered around 0 V because the probe (with its high input impedance, typically 1&ndash;10 M&Omega;) effectively provides a DC path to ground. That&rsquo;s what allows the capacitor to block the DC component and the output to &ldquo;float&rdquo; to a proper AC-centered signal. 
 As for LTspice v24.0.8, I'm just a user myself, so I don't know exactly how the developers handled floating nodes in that version. But it seems the simulator may have implicitly assigned some weak reference, giving the appearance of correct DC blocking even without a defined load. In the newer versions, this behavior appears to have become more strict or realistic &mdash; if there's no DC path, the node floats as it would in reality. 
 To replicate real oscilloscope behavior in LTspice, you can add a large resistor (e.g., 10 M&Omega;) from R3 to ground. This simulates the effect of the oscilloscope's input impedance.)

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Capacitors not removing DC component after new update.