[help] understanding Op-Amp frequency characteristics

[bombo]

Hi

I need help understanding the frequency characteristics of operational amplifiers. I do not understand why the output of an Op-Amp behaves much differently when the frequency of the input is increased.

For example during the lab when the input to an inverting Op-Amp circuit was a sine wave.
At 1kHz it behaved as normal.
At 50kHz the output was not inverting anymore but triangular-like instead, as shown in the picture. Could anyone explain why the output behaves like this?

 

[Svein]

This is called slew rate limiting and is part of the OpAmp specification.

 

[bombo]

This is called slew rate limiting and is part of the OpAmp specification.

Ok thanks for your answer Svein. I have never heard of "slew rate" but I will look into it :D

 

[LvW]

Slew rate is a large-signal parameter that describes the ability of the output voltage to follow the input voltage - indpendent on the gain (which is a small-signal parameter).
That means: When you drastically decrease the input (and, therefore also) the ouput voltage you should see that the triangle waveform returns to a sinusoidal form (when the peak amplitude is small eneough)