Jackson1223:
HiI have an input signal which is about 0,21v at max. I want to use the arduino to read it, right now I have it set to internal reference so it can but not accurate.
My tough was to use a opAmp so i bought a LM1458N. The problem is using it. I guess i want non inverting, but how can i limit it to 0-5v?
The signal comes from a ultrasonic transducer btw.
5V / 0.21V ~ 23.8
So use a gain of less than or equal to 23.8 and your output will not exceed 5V. Of course that will not work with the 1458 which can not approach its supply rails, so you would need to power the 1458 with greater than 5V (progrably at least 6-7V) to get 5V out and if you want 0V (or less than about 1V?) you would need a bipolar supply as well.