Other Parts Discussed in Thread: OPA140, OPA2132, OPA197, OPA192
Hi:
There is a problem about the use of OPA4140, please help to confirm:
Three of them are used as amplifiers and the other as voltage follower.Attached are the circuits and waveforms of the nodes in question.
Problem description:
The problem lies in the last stage of the follower. There is no noise in front of the follower, but there is noise behind the follower.
A few notes:
1. There is no relation between the noise of the follower and the output load.
2. From the waveform observation, the appearance of noise has no relation with the input frequency.
3. From the perspective of several noisy waveforms, the noise occurs at a certain specific voltage, and the noise is triggered only when the signal voltage rises or falls at this point.
4. Replace the last level follower with a separate OPA140, and the problem remains the same
5. Replace the last level follower with OPA2132 to eliminate noise.
The schematic diagram is as follows:
oscillogram：
