OPA2376: What is the maximum capacitor value can be driven by OPA2376 for low pass filter circuit?

Kazuya Nakai59

Guru 20100 points

Part Number: OPA2376

Hello guys,

One of my customers is evaluating OPA2376 with low pass filter circuit like the follow.

https://www.avrfreaks.net/forum/why-simple-op-amp-low-pass-filter-does-not-work

The customer parameters are the follow.
R1 = 1k ohm.
R2 = 68k ohm
C = 0.01uF

But they want set the filter cut-off frequency lower than the above.

At this moment, they have the following question.

Q. What is the maximum capacitor value can be driven by OPA2376 for the low pass filter circuit?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 2 years ago

0 kai klaas69 over 2 years ago

Guru 140200 points

Hi Kazuya,

according to the phase stability analysis the circuit would be stable from 100pF to at least 10000µF:

kazuya_opa2376_1.TSC

But due to imperfections like finite output impedance of OPAmp at higher frequencies, the low pass filtering performance is rather poor:

kazuya_opa2376.TSC

It would be way better to do the low pass filtering with a passive low pass filter or at least to add a passive low pass filter to enhance the filtering performance at the higher frequencies.

There's another issue: When powering down the OPAmp abruptly the filter cap has stored enough energy to destroy the OPAmp during discharging via the internal ESD protection diodes at the inputs and output of OPAmp. So you would need to add a current limiting resistor in series to the input. Like this, for instance: