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Collin Wells

Our monthly post on our sister blog, the “Precision Hub” on Planet Analog, focuses on transient stability testing.

In it, I share a recent experience I had with one of our summer interns. He was taking transient stability data on a design and learned an important lesson – the step size of the output signal is extremely important to achieve accurate results.

Read my full post, "Transient stability testing: Watch your step," on Planet Analog to learn how I helped him identify the issue and correct it.

Anonymous

  • It has been a while since I last looked at percent overshoot vs. phase margin, but it would be interesting to include an excel calculator for those who like the math abuse.

    It would also be interesting to note for readers that this particular test presumes a 2nd order system that is not slew rate limited (you did mention slew rate briefly).

    -Ken

  • Basically you need to provide the correct resistance to ground to "terminate" the signal as it enters your circuit to prevent unwanted reflections or distortion.  The termination resistance will be specified for each instrument or tool but will usually be 50 or 75 Ohms.  I was able to find some useful information with a web search.  Try searching for "50 Ohm Termination"

  • Sorry again. I am new to 'termination resistor' concept. Can you please tell me from where I can get to know about this termination resistor. I tried to google about the topic, but didn't get anything. I

  • Hi Deepak,

    The source in the schematic represents a standard lab function generator with an internal 50 Ohm resistance in series with it's output, which is not shown.  The 50 Ohm resistor on the schematic is used to terminate the 50 Ohm output of the generator.  If you don't include the termination resistor you'll find the input to your system is twice as large as the function generator is set to unless you change the output termination of the generator to Hi-Z.  

  • What is that 50 ohm resistor in parallel with the source? If it is the internal resistance of the source it must be in series with it. But it is in parallel.