Amplifier configuration problems

Thread Starter

Kullis97

Joined Feb 2, 2021
1
Hi, I am going to amplify the signal from a pH sensor, this signal is to be read by an MCU, so I do not have a larger spectrum than 0-3.3V, I, therefore, want the signal to oscillate approx. at 1.5V, but when I amplify this signal the whole signal is lifted, instead of it still oscillating at approx. 1.5V, does anyone have a solution to this problem?

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Last edited:

MrChips

Joined Oct 2, 2009
23,515
How is your pH sensor managing to generate a sinewave - that is fascinating!
This is not a live circuit. It is a simulation with a 1Hz sine input.
I guess what the TS means is he wants to offset the signal by 1.5V DC.

The solution is you amplify the pH signal first then apply the 1.5V DC offset.
 

Audioguru again

Joined Oct 21, 2019
3,173
Your opamp is biased at half the supply voltage but it has a gain of 2 times so of course the output is saturated at +3.3V and it rectifies the signal.
Also, your circuit has an unknown reference voltage that will also be amplified.

Your opamp is DC-coupled therefore it amplifies DC. Use coupling capacitors if you do not want the DC amplified.
 
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