Human body bioelectric signal preamplifier composed of INA102

As shown in the figure, this is the human bioelectric signal preamplifier circuit. In medical instruments, it is often necessary to measure the human bioelectric signals, such as electrocardiograms, electroencephalograms, etc. Since the bioelectric signals are very weak, the requirements for the amplifier circuit are very high. This circuit uses the low-power instrument integrated operational amplifier INA102. The characteristics of the integrated chip INA102 are: small static current (maximum 750μA); the internal gain can be changed through different connections of the pins, and the selectable gains are: 1, 10, 100 and 1000. In the figure, pins 4 and 7 are connected and pins 5 and 6 are connected to obtain a maximum gain of 1000; high gain accuracy and small drift (maximum 5×10-6/℃); high common mode rejection ratio (minimum value is 90dB); small offset voltage (maximum value is 100μV); small nonlinear distortion (maximum 0.01%); small drift of offset voltage (maximum value is 2μV/℃); high input resistance (1010Ω). The voltage amplification factor of this circuit is 1000, and its output peak-to-peak voltage can reach 1V.