hello, i trying o do an electrocardiogram but i need an amplifier to capture signal of the body. Someone could tell me where found that schematic? if had printed files is better... thanks for help
There are lots on line, this is typical:- http://blog.makezine.com/archive/2007/03/home_made_electrocardiogr.html
For ECG (and especially EEG), you are going to want to use what are called "instrumentation amplifiers"; these are essentially op-amps, but specially designed for safety, as well as stability and noise rejection (to a point).
They also tend to be fairly expensive compared to standard op-amps (Steve Ciarcia had a project for a homemade EEG machine; the IAs he used were pretty expensive and the project used several - but it was still waaay cheaper than purchasing an EEG machine in the 1980s, and you weren't likely to build an impromptu shock therapy machine, either).
It is possible to get away with using standard op-amps for ECG (I know I have seen such projects), but if anything went wrong...
The link below might be of interest to you: