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  • Author Author: tariq.ahmad
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Learn Three Ways You Can Create Bode Plots - Workbench Wednesdays 64

Creating a bode plot from a simulation (or transfer function) is easy. But what if you want to create a bode plot for a REAL op-amp circuit or filter? One way is to measure a few parameters with an oscilloscope and function generator and then put those into a spreadsheet. Another is to use network analysis or frequency response analysis to do it automatically!

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Bill of Material:

Product Name Manufacturer Quantity Buy Kit
LM358 - Audio TI 1 Buy Now
TL081 - JFET General Purpose, 4 MHz SOIC-8 ST Microelectronics 1 Buy Now
Bench Oscilloscope - 200 MHz, 1 GSa/s, 14-bit, AFG, DMM Multicomp Pro 1 Buy Now
[Bundle] Development Kit, Analog Discovery 2 Pro Bundle, 30MHz Oscilloscope, 12MHz Waveform Generator Digilent 1 Buy Now
MXO4 - 4 Channel Oscilloscope 200 MHz Rohde & Schwarz 1 Buy Now
 

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  • in reply to baldengineer

    The output waveform shouldn't dance around. I think if you look at an FFT of the output, the amplitude of your test tone will be the correct amplitude. And, you will also see and there is also something else present. I don't know if its oscillating at a lower frequency...

    If you were to probe your op-amp's output with a 1x scope probe, the measured bode plot with gain peaking is entirely plausible. But, I am pretty sure you are using 10x probes.

    Still, I blame the intern Slight smile and great video!

    *had to delete to edit*

  • in reply to scottiebabe

    On the LM358, there was peaking with X1 probes. The TL081 peaked with both X1 and X10.

    I'll give the output a little more scrutiny next time I'm in the lab. You have me curious about what I missed. I had several setups going on, so I might be mixing up scenarios.