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Basic Operational Amplifiers
18 questions By Tony R. Kuphaldt
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Question 16 of 18
What does it mean if an operational amplifier has the ability to “swing its output rail to rail”? Why is this an important feature to us?
Reveal answerBeing able to “swing” the output voltage “rail to rail” means that the full range of an op-amp’s output voltage extends to within millivolts of either power supply “rail” ( V and -V).
Challenge question: identify at least one op-amp model that has this ability, and at least one that does not. Bring the datasheets for these op-amp models with you for reference during discussion time.
Notes:Discuss what this feature means to us as circuit builders in a practical sense. Ask those students who tackled the challenge question to look up the output voltage ranges of their op-amp models. Exactly how close to V and -V can the output voltage of an op-amp lacking “rail-to-rail” output capability “swing”?
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Question 17 of 18
A very important parameter of operational amplifier performance is slew rate. Describe what “slew rate” is, and why it is important for us to consider in choosing an op-amp for a particular application.
Reveal answer“Slew rate” is the maximum rate of voltage change over time \(\frac{dv}{dt}\) that an op-amp can output.
Notes:Ask your students why [dv/dt] might be an important parameter in a circuit? In what application(s) might we need the op-amp to “swing” its output voltage rapidly? In what application(s) might we not care about the op-amp’s slew rate?
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Question 18 of 18
Some precision operational amplifiers are programmable. What does this feature mean? In what way can you “program” an op-amp?
Reveal answerA “programmable” op-amp is one with extra connections to its internal circuitry allowing you to set the current source values using external components.
Notes:What possible benefits are there to “programming” the current source values in an operational amplifier? Discuss this with your students, asking them to share what they’ve found through their research.
