A new Schmitt trigger with adjustable hysteresis using floating-gate MOS threshold inverter

A novel adjustable Schmitt trigger using multiple-input floating-gate MOS(FGMOS) threshold inverter is presented. The simple circuit consists of one n-channel FGMOS, one p-channel FGMOS and a conventional CMOS inverter. The different hysteresis voltages can be achieved by varying the ratio of capacitive coupling coefficients. By only changing the values of external input control signals, the hysteresis window can be conveniently moved without varying its width. HSPICE simulation results using TSMC 0.35μm double-poly 4-metal CMOS process parameters have verified the effectiveness of the proposed approach. The simulation results show that the discrepancy of hysteresis voltages between the theoretical and simulated results is smaller than 3%.