Stabilized Wide-Band Potentiometric Preamplifiers

The need for a wide-band preamplifier to measure bioelectric potentials from a source with high internal resistance and shunt capacitance has stimulated the development of instruments which should be generally useful. Consideration is given to the simultaneous attainment of such factors as low grid current, linearity, low drift, and improved dynamic response by compensation for input capacitance. An analysis of a simplified circuit is augmented by the use of an analog computer to simulate the system for a preamplifier having either a first- or second-order response. Some examples of circuits suitable for bioelectric measurements are described. It has been possible to chopper-stabilize such preamplifiers against drift without significant degradation of their high input impedance characteristics.