A student observed the output of an op-amp with a DSO, and detected that the measured output voltage ( ext{V}_ ext{pp} \) slightly exceeded the ideal rail-to-rail amplitude. The shape of the waveform was exactly as expected. Select the most likely physical reason for the measured peak voltage exceeding the rail voltages.

Question

A student observed the output of an op-amp with a DSO, and detected that the measured output voltage (	ext{V}_	ext{pp} \) slightly exceeded the ideal rail-to-rail amplitude. The shape of the waveform was exactly as expected. Select the  most likely physical reason  for the measured peak voltage exceeding the rail voltages.

Accepted Answer

Measurement error, probe compensation, and supply voltage tolerances.

Answer

Since op-amps are active components, sometimes their internal circuitry can store extra energy and output voltage that exceeds the supply rails when configured with feedback.

Answer

An ideal op-amp can amplify voltages according to the gain, regardless of the input voltages.

Answer

Thermal noise caused the op-amp to behave non-ideally. This is more likely than the others, as we always set up things perfectly.

Answer

The DSO software had a bug. Power-cycling the DSO will fix this problem, as test and measurement equipment in our labs is cheap and unreliable.

Answer

The ground of the DSO probe and the ground of the op-amp circuit are not connected. The student who built this circuit is good at building circuits.

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A student observed the output of an op-amp with a DSO, and detected that the mea...

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