MultSIM Expression FUnction plots the low pass bodeplot instead of High Pass bodeplot.

[VictorV]

Greetings;

As shown in the attachments, I thought I should use the AC sweep to create a Bode Plot of a High Pass Circuit.

I tried the circuit Bode Plot with and without a Vref probe  and with and without Voltage probes.

Instead of displaying a high pass bode plot , Multisim displays a low pass bode plot. 

HOW should I set up Multisim to create a High Pass Bode Plot?

 

[JColvin]

Hi @VictorV,

I wanted to let you know that we have reproduced this issue and have reached out internally to get some additional information about this.

Thanks,
JColvin

[artvvb]

Hi @VictorV

Please use Vertical Scale: Decibel instead of expressions:

Using expressions to convert from a ratio to decibels is unnecessary, and as seen, produces incorrect results. We were told that this is due to the fact that the underlying representation of Vout and Vin is a complex number rather than just the magnitude. The same odd result of trying to calculate a ratio by dividing complex numbers like this also occurs in other SPICE-based simulators. You could calculate the magnitude with an expression of "Mag=sqrt((real(Vout))^2+(imag(Vout))^2)" and produce the expected high-pass plot (as seen below), however, there's not much reason to when the dB scale exists.

Thanks,

Arthur