  ### Author Topic: LTspice ac analysis to determine stability of op-amp circuits  (Read 4785 times)

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#### mmilejski

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• Posts: 25
• Country:  ##### LTspice ac analysis to determine stability of op-amp circuits
« on: January 12, 2014, 09:37:08 am »
What about a video where Dave would show how to conduct an in depth analysis of some op-amp circuit prone to oscillation, including:
modeling test jig
an introduction to Bode plotting
common ways to reduce oscillation in op-amp circuits
using step function to choose right values for resistors and capacitors in feedback loop

I hope that is a good idea Maybe someone can post a link to existing video or document?
I already saw LT video on it, but it is short and does not explain Bode plots, just assumes viewer knows it.

#### Jay_Diddy_B

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•   • Posts: 2212
• Country:  ##### Re: LTspice ac analysis to determine stability of op-amp circuits
« Reply #1 on: January 12, 2014, 11:14:08 am »
Hi,

I have a look at his thread:

A Bode plot is the plot of the frequency response of a system versus frequency. The plot can show just amplitude or amplitude and phase.

The Bode plot is normally plotted with Log amplitude in dB on the y-axis and Log Frequency on the X-axis.

A single pole filter low pas filter will have a slope of -20dB per decade of frequency.

Bode plots are very effect for control loop analysis.

Before PCs, I used to solve control loop problems by drawing the various elements on Log-log paper.

Have a look at this:

http://en.wikipedia.org/wiki/Bode_plot

It is a bit over-the-top, in the mathematical department.

Regards,

Jay_Diddy_B

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