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A Differential Current-to-Time Interval Converter Using Current-Tunable Schmitt Triggers

  • Chung, Won-Sup (Dept. of Semiconductor Engineering, Cheongju University)
  • Received : 2017.11.30
  • Accepted : 2017.12.20
  • Published : 2017.12.31

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 $726.9{\mu}s/pH$ over pH variation range of 2-12 and a linearity error less than ${\pm}0.05%$.

Keywords

References

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