0.4-V Ultra-low-voltage Pseudo-differential CMOS Schmitt Trigger Based on Digital Inverter

In this paper, a digital pseudo-differential Schmitt trigger with very low supply voltage is proposed. The proposed Schmitt trigger is design by exploiting the design procedure of an analog Schmitt trigger. It is implemented only using digital CMOS inverters which is composed of a pseudo-differential comparator consisting of two CMOS inverters and a cross-coupled inverter pair as positive feedback. The proposed circuit is the only digital Schmitt trigger which operates in fully-differential mode that has simultaneously two outputs of non-inverting and inverting and its hysteresis center can be changed by the input voltage. The proposed Schmitt trigger is simulated in 0.18 um CMOS process with 0.4 V supply voltage. Due to the very low number of transistors, the proposed circuit occupies 10×9.8 μm2 chip area and consumes only 6.64 nW power.