Publications:
The Biomedical Engineering Handbook: Second Edition.
Ed. Joseph D. Bronzino Boca Raton: CRC Press LLC, 2000
Very detailed chapters on the transducers and amplifiers necessary to record human biopotentials. Several chapters can be found online. Of particular interest is Chapter 70: Biopotential Amplifiers.
Thakor, NV. Biopotentials and Electrophysiology Measurement.
In The Measurements, Instrumentation and Sensors Handbook. Ed. Webster, JG. CRC Press.
A well-explained and illustrated, but somewhat cursory, overview of the characteristics of various biopotentials (ECG, EEG, EOG, EMG) and the instrumentation required to measure them. Includes discussions of both the transducers and the amplifiers required, with basic schematics. Freely available online; as I’m not sure of the copyright restrictions, I won’t suggest specific sources, but a quick search should locate the paper easily.
Yazicioglu RF, Hoof C van, Puers R. 2009. Introduction to biopotential acquisition. In Biopotential readout circuits for portable acquisition systems. Springer. http://www.springer.com/978-1-4020-9092-9
Neuman, M.R.; Chapter 5, "Biopotential Electrodes" and Chapter 6, "Biopotential Amplifiers",
In Medical Instrumentation: Application and Design, Ed. Webster, J. G., Houghton Mifflin, Boston, Massachusetts. 1978.
Very detailed chapters on the design considerations for biopotential transducers and amplifiers. Somewhat dated, but still quite useful.
Websites:
http://www.egr.msu.edu/classes/ece445/mason/files/7-BioAmps_ch6.pdf
http://users.rowan.edu/~polikar/CLASSES/ECE404/Lecture11.pdf
ftp://tdata.atu.edu/Lakshmisudhakar.Kondeti/ecg/Bioamplifiers-2005.pdf
http://faculty.ksu.edu.sa/.../Part%202%20Amplifiers%20%20Applications.ppt
Several Power Point type lecture presentations on the electronic characteristics of amplifiers used to measure human biopotentials.