Amplifiers for bioelectric events: a design with a minimal number of parts.

A design for an amplifier for bioelectric events is presented that has fewer parts than conventional designs. The design allows the construction of amplifiers of a high quality in terms of noise and common mode rejection, with reduced dimensions and with a lower power consumption. Gain, bandwidth and number of channels are easily adapted to a wide range of biomedical applications. An application example is given in the form of a multichannel EEG amplifier (gain is 20,000), in which each channel consists of three operational amplifiers (one single and one dual), six resistors and two capacitors. The equivalent input noise voltage and current are 0.15 microVrms and 1 pArms, respectively, in a bandwidth of 0.2-40 Hz, and a common mode rejection ratio of 136 dB is achieved without trimming.

Patient isolation in multichannel bioelectric recordings by digital transmission through a single optical fiber.

A design for patient isolation in 64-channel ECG recordings is presented. Small dimensions of the isolated section and the use of an optical fiber as the only connection between the isolated section and the grounded section of the measurement system ensured a minimal capacitance between the patient and the environment. The consistent low-power design of the isolated section resulted in a power consumption of 210 mW, which enabled a 10 h continuous operating time of the battery powered isolated section. The system handles 64 signals with a dynamic range of 75 dB. Analog to digital conversion is performed in the isolated section with a sample rate of 1 kHz per channel. The receiver interfaces to a commercially available DMA board for a standard personal computer.