square wave oscillator bode plot

[james0ne]

hi, im trying to use the simulate ac analysis function in multisim with my circuit, but i cant seem to get anything out for my bode plot, i've tried other oscillator circuits dont seem to work as well, can anyone help?

 

[crutschow]

It looks like you have an oscilloscope connected in the circuit, not a Bode plotter.

You can only do Bode plots of the sine-wave response of the input versus output of a network. For that you need a sine-wave source at the input to the circuit.

A bode plot of an oscillator makes no sense since it has no input. What would you expect a Bode plot of an oscillator to show?

 

[james0ne]

ahh.. i see well my professor wants us to make a frequency response for that circuit, i know thats a scope, previously i can simulate a bode plot without placing one right into the circuit by using the ac analysis function

 

[crutschow]

I believe the AC analysis still requires an AC source at the input to the circuit.

 

[james0ne]

very good point, how can i create a bode plot, and what is the best way ?

 

[crutschow]

You can't really do a Bode plot of a square-wave oscillator that is built from a device such as the 556. The Bode plot is an AC analysis with sine-waves and it assumes a linear circuit. Square-wave generators are non-linear and thus can not be analyzed that way.

Normally you inject an AC signal at the input of the circuit and then measure the output response over frequency. The gain is usually plotted in dB versus frequency. Typically the phase difference between input and output is also plotted versus frequency. I believe multisim has a Bode plotter that does both simultaneously.

 

[james0ne]

ok thanks for the explanation i think i get it now