Editor's Note: In 2007, we published a four-part series on bypass capacitors and decoupling that was very popular with the design audience (links below). Now, one of the authors of Part 4, Kendall Castor-Perry, extends the series with six more sections which explore interactions between supply and capacitor, capacitor materials, and simulation models. This very practical extension blends theory and measurements, and its lessons not only will improve your knowledge but help you minimize problems, some of which can be very subtle and difficult to diagnose and solve.
For various reasons, they are presented to you as linked pdf files, one per week, with the corresponding section links added in successive weeks.
And a big "congratulations" to you if you have gone through all five preceding sections of Part 5 (and any of Parts 1 through 4); you are on the last lap. You've invested a lot of time that will hopefully have a big payback!:
Part 5.1: "The regulators interaction with capacitors": The interaction between the power-supply regulator and the decoupling (bypass) capacitor is explained. In addition, the overall impedance seen by the IC, including capacitors, PCB traces, and voltage regulator is assessed; click here
Part 5.2: "Ring the changes, change the rings": Ringing and other voltage transient effects examined with a small test-current step, as well as effect of capacitor dielectric, click here
Part 5.3: "Some gain, some pain": How coupling affects, and bleeds through, to op amp output; click here
Part 5.4: "Don't get into a macromuddle": Inaccurate op-amp simulation macromodels can lead to misleading results on the effect of bypass capacitors in decoupling applications, click here
Part 5.5: "When Harry regulator met Sally op amp": Examine the signal chain from op amp to load, and the interaction of load current, power supply, and amplifier output, click here
Part 5.6: "Steering in the right direction": Validated simulations and macromodels provide an approach to proper selection of bypass decoupling capacitors in op-amp and other circuits, click here
You can read the previous parts by clicking on the corresponding link:
Part 1: "Choosing and Using Bypass Capacitors," click here
Part 2: "Choosing and Using Bypass Capacitors," click here
Part 3: "Choosing and Using Bypass Capacitors,"click here
Part 4: "Know the sometimes-surprising interactions in modelling a capacitor-bypass network," click
About the author Kendall Castor-Perry has been practicing the electronic arts for over three decades, having designed industrial instrumentation, communications systems and audio circuits. He spends much of his time helping people to solve complex signal-path problems with both empathy and rigor.
Without even thinking about it, consumers depend on technology throughout the day as they send texts, turn on lights, and drive home from the office. But that technology depends on something that usually goes unnoticed until there's a problem.
I thought it would be good to continue looking at the example I gave in my last blog where we looked using fewer LDOs and combining power supply rails on an ADC while maintaining isolation with ferrite beads.
Electronic equipment and power management is becoming increasingly critical as our power grid ages and renewable energy comes on line. In response, new technologies are being developed to protect equipment from power disturbances and fluctuations.