A Low-Cost Multichannel Preamplifier for Physiological Signals

A preamplifier for physiological signals (ECG, EMG, etc.) is described for general use in mnltichannel applications. The limited number of components made it possible to implement eight channels on one Eurocard printed circuit board (160 x 100 mm) and 64 channels in a 9.5 in cabinet in a cost-effective manner (about $ 50 per channel). The use of a monolithic instrumentation amplifier based on the current feedback principle resulted in high dc suppression combined with excellent noise performance and high common mode rejection. A second-order Butterworth low-pass filter was implemented using switched capacitor circuits, so that in a multichannel setup the rolloff frequency of all channels can be (digitally) controlled by one clock frequency.