Similar topics
Recommended
Bruce Trump

You have voted. Unity-gain-stable op amps won in a landslide—they’re far more popular than decompensated op amps. What’s this all about?

Click Here to read on EDN Magazine site.

Anonymous

  • Hi Bruce,

    I have a question: How to examine the stability of uncompensated op amps employed in DAC-buffering I/V converters? Take the OPA637 for example, it will be stable when its noise gain is greater than 5, but when it comes to noise gain, it represents a "voltage gain", and transimpedance amplifiers do not have voltage gains, so what's the condition makes these kind of configurations stable?

    I have some ideas: G>5 means β<1/5. From the voltage point of view, the input impedance of this inverting configuration is 0, so β=0 thus the op amp will be always stable. From the transimpedance point of view, the β of a transimpedance amplifier is 1/(feedback impedance) so to make op amps stable we should use feedback resistance greater than 5 Ohm. Which is correct?

  • Thanks for your observations, Bruce, they are quite useful. I can confirm them for OPA637 / OPA627.