The design and construction of an amplifier for bio-electric recording

The requirements to be fulfilled by an amplifier to be used for bio-electric research are discussed, and certain suitable circuits are described in outline, together with considerations relating to the limits of amplification obtainable in practice. An amplifier fulfilling the necessary requirements is described, and details of its performance are given, indicating the advantages of negative feedback obtained in the reduction of drift inherent in d.c. amplifiers.