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OPA188: Oscillation

toshi-e2e
Genius 4735 points
Part Number: OPA188
Other Parts Discussed in Thread: OPA171, OPA277, OPA196, OPA197, OPA191, OPA192

Hi all,

My customer is trying to realize a circuit that uses OPA188 to full-wave rectify an AC waveform, integrates it in the subsequent amplifier, and outputs DC proportional to the input amplitude.
When inputting a signal of Vpp = 300mV and 20kHz to a rectifier circuit, an oscillation-like waveform is observed.
Why does this oscillating waveform occur?

The red waveform is the input waveform.
The blue waveform is the offset voltage waveform.
Yellow is the output of OPA188.
Green is the waveform after rectification.

In addition, such oscillation waveforms were not observed with OPA277 and OPA171.

I would like to send the circuit diagram via private email later.

Regards,

Toshi

  • 0
    TI__Guru 61430 points

    In order to minimize the input offset voltage, OPA188 is a chopper stabilized amplifier as such is not the best op amp to implement a full-wave rectifier of AC signal.  OPA191, OPA192, OPA196 or OPA197 would be a better choice.   Having said that, in order to assist you what causes the oscillation we would need to see your circuit schematic including supply voltage used.

  • +1
    TI__Guru 61430 points

    Hi Toshi,

    I have received your email with detailed circuit schematic and will directly reply to it.  For this reason, I'll close this E2E inquiry.