Greetings,
I'm working on a a project to measure heartbeats rate, I've been following instructions from this link (https://maker.pro/pcb/projects/diy-ecg-build-electrocardiogram), I've noticed this in schematics ( https://maker.pro/storage/1681624/16816246c675467da8cefbe1341a1dd4.jpeg ) the LM358 amplifiers is written on it U2A, U4A . Does it mean it's the same amplifier or a different one ?

 

Hello,

U2A and U2B are one LM358.
U4A and U4B is a second LM358.

For more details, you could ask @Robin Mitchell , the maker of the circuit and member of this forum.

Bertus

 

Hello,

U2A and U2B are one LM358.
U4A and U4B is a second LM358.

Bertus

That's great. I've found the datasheet for the amplifier ( http://www.ti.com/lit/ds/symlink/lm158-n.pdf ) and it seems to contain 2 internal op-amps, is it fine to wire them normally as shown in the schematics of the project or a different method ? thank you.

 

Yes wire them "normally" as independent devices.

Regards, Dana.