A Differential Current-to-Time Interval Converter Using Current-Tunable Schmitt Triggers
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A differential current-to-time interval converter is presented for current mode sensors. It consists of a ramp voltage generator, a current mode sensor, a reference current source, two current-tunable Schmitt triggers, a one-shot multivibrator, and two logic gates. The design principle is to apply a ramp voltage to each input of the two current-tunable Schmitt triggers whose threshold voltages are proportional to the drain current values of the current mode sensors. A proposed circuit converts a current change in the ISFET biosensor into its equivalent pulse width change. A prototype circuit built using TSMC 0.18 nm CMOS process exhibit a conversion sensitivity amounting to 726.9 ㎲/pH over pH variation range of 2-12 and a linearity error less than 0.05 %.
Abstract
A differential current-to-time interval converter is presented for current mode sensors. It consists of a ramp voltage generator, a current mode sensor, a reference current source, two current-tunable Schmitt triggers, a one-shot multivibrator, and two logic gates. The design principle is to apply a ramp voltage to each input of the two current-tunable Schmitt triggers whose threshold voltages are proportional to the drain current values of the current mode sensors. A proposed circuit converts a current change in the ISFET biosensor into its equivalent pulse width change. A prototype circuit built using TSMC 0.18 nm CMOS process exhibit a conversion sensitivity amounting to 726.9 ㎲/pH over pH variation range of 2-12 and a linearity error less than 0.05 %.
참고문헌 (7)
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- Y. H. Ghallab, "A novel pH sensor using differential ISFET current mode read-out circuit", MEMS, NANO and Smart Systems, 2003. Proceedings. International Conference on, pp.255~258 (2003)