I just recently bought a OPA350 OP-AMP due to its fast recovery speed that I need for my application (Precision Rectifier), it just arrived today and I went to go test the circuit. However weir behavior is starting to surface at high frequencies...but this time it's the Vpk-pk.

Datasheet: OPA350

Output at 584 Hz

Frequencies of (100Hz-10kHz)

Output at 21 kHz

Frequencies of (20kHz)

As you can see the \$Vpk-pk\$ took a beating at 20kHz and I thought this was due to the bandwidth of the OP AMP, however it's stated to be 30MHz. It also gets much noisier as well.



so the flatness should decade 6dB/sec after 30MHz ish, but why is it doing it around 20kHz?


\$SR = 20kHz*2*\pi\$
\$SR = 0.127V/uS\$

The OP AMP is rated for 22V/uS



simulate this circuit – Schematic created using CircuitLab

  • 1
    Have you checked the slew rate? That's often a gotcha – Scott Seidman Jul 5 at 15:36
  • Its more than enough :/ its faster than my old OP AMP which was slower.. the Slew rate is at 22V/uS should be more than enough. – Pllsz Jul 5 at 15:37
  • 1
    Try putting a 1 kohm load after the diode to 0 volts. – Andy aka Jul 5 at 15:49
  • 1
    My MacBook and iPhone is attenuating it’s signals at higher frequencies . Ahaha thought it was my op amp sorry guys. – Pllsz Jul 5 at 16:08
  • 1
    It's worth noting that your negative excursion of the input signal is taking the input below gnd by more than recommended. I'd also replace the In4148 with a much lower Vf diode to get more signal output capability. This may help: ww1.microchip.com/downloads/en/AppNotes/01353A.pdf – Jack Creasey Jul 5 at 16:26

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Browse other questions tagged or ask your own question.