Current sensor for biomedical measurements

摘要

A current sensor for biomedical measurements comprises switched capacitors 103 & 105, in series across amplifier 101, and switched capacitor network 120 between amplifiers 101, 111. Switches 107 & 109 may be controlled by complementary clocks (A, B: 211, fig. 2), e.g. switch 107 being closed while switch 109 is open so capacitor 103 is reset while 105 charges. The clock signal occurs when charging current passes a threshold determined by comparators (201 & 203, fig. 2). When input current is small and higher frequency amplifier output 111, being linearly related to input current in dependence on the capacitances involved, provides a low noise current measurement. For relatively larger current, flip-flop outputs (207 & 209, fig. 2) provide a frequency output proportional to input current. The dynamic range is therefore widened. Since no external reset or sample clock is required, bandwidth is not limited by sample rate.