I'm having a problem with a high pass filter, maybe someone has an idea how to fix it.
Initially I have an IC that provides a sinusoidal signal of approximately 0 to 3V positive with a frequency varying between
50KHz and 100KHz (Figure 1).
Figure 1
The purpose of my high pass filter is to remove the DC component, leaving at the end the signal varying between approximately + 1.5V and -1.5V with the same frequency range (Figure 2).
Figure 2
I am using a Basic RC circuit with an op amp (TL081) as a buffer, and with symmetrical power supply of + 5V and -5V. The cutoff frequency is 100Hz (Figure 3).
Figure 3
My problem is that on the output of my op amp (Vout) I have a triangle wave (Figure 4).
Figure 4
The signal in "Vout" in the Figure 3 is a triangle wave with Vpp ranging from 0 to + – 1.5V and with the desired frequency (50KHz to 100KHz).
An interesting detail is that before the opamp ("Vt" in the Figure 3) the signal is correct, ie in "Vt" the signal is a sine wave of 1.5Vpp with frequency from 50KHz to 100KHz.
All observations were made on a real circuit with an oscilloscope.
Anyone have any idea what happens to my Op Amp?
* UPDATE
I did some tests with a power supply of + -15V.
And the results were the same, according to the oscilloscope images below:
at "Vt" in Image 3:
at "Vout" in Image 3:
Best Answer
Have a look at the TL081's slew rate - the maximum rate of change of the output or \$ \frac {dV}{dt} \$ but it is 13 V/µs quoted at +/-15 V supply.
Now have a look at your output. Your \$ dV \$ = 3 V and at 50 kHz one half cycle will be \$ \frac {1}{2} \frac {1}{50k} = 10 \mu s \$ giving you \$ \frac {dV}{dt} = \frac {3}{10µ} = 0.3 \; V/µs \$ and 0.6 V/µs at 100 kHz.
The figures indicate you should be OK at +/-15 V but maybe not at +/-5 V. If you can drop your frequency by a factor of 10 and see if that solves the problem you might start to get better insight.