Opa Alice build noise floor

[oscarhuang]

@oscarhuang : can you share the exact schematic of your circuit? In the original OPA Alice circuit, there are two elcaps that would effectively eliminate zener noise. The ones encircled in the picture.

Jan
View attachment 138829

This is a picture of my Alice OPA. I removed the zener diode. The noise is reduced a lot. Previously I found the noise level to be too high and unusable, but after removing D1 the noise decreased. But what I prefer is Mr. Rogs' OPA1641 circuit. I set the polarization voltage to around 60V. Very, very quiet, thank you Rogs for your selfless sharing.

 

[oscarhuang]

Practice is the best teacher. Here is the voltage I measured. The voltage before the 200 ohm resistor is 21.7V, and after the 200 ohm resistor it is 20.9V. So it is far lower than the limit voltage of the op amp. Even if the zener diode is removed, I don't think it will damage the op amp.

 

[Cqwet Dbdfte]

"The Phantom Menace" , sounds like a B-movie.
Supposedly sharp knee zeners have more noise than the soft ones.
A voltage surge from plug in could be from a "race condition" between the local storage cap charging up and the current risetime on the OP amp.