I found the input voltage drops around 2V drop (observed from oscilloscope) when I connect the ion mobility spectrometer (IMS) signal to the circuit "an improved precision rectifier circuit", like the attached picture.
I have already used single supply +5V from Arduino Due and dual supply +-15V, but the problem still existed.
Can someone help me to deal with this problem?
I modify some parts to what you suggested. I still have some problem with my circuit. I have the positive and negative signal from the signal source. The first LM358 I use it as voltage follower. Second LM358 I use it as inverting signal circuit, and I can get the peak what I want. But I need to remove up to -4 to -5V and amplify positive signal from second LM358 output. When I use the third LM358 as below, the positive signal is amplified but the negative signal also amplified. Can I have some way to remove negative signal and let the positive signal be amplified?
Second question is I found the signal decrease before first LM358 like picture shown below when I connect the wire between Arduino and signalinput.