A Sub-Threshold Differential CMOS Schmitt Trigger with Adjustable Hysteresis Based on Body Bias Technique

Abstract

This paper presents a sub-threshold differential CMOS Schmitt trigger with tunable hysteresis, which can be used to enhance the noise immunity of low-power electronic systems. By exploiting the body bias technique to the positive feedback transistors, the hysteresis of the proposed Schmitt trigger is generated, and it can be adjusted by the applied bias voltage to the bulk terminal of the utilized PMOS transistors. The principle of operation and the main formulas of the proposed circuit are discussed. The circuit is designed in a 0.18-μm standard CMOS process with a 0.6 V power supply. Post-layout simulation results show that the hysteresis width of the Schmitt trigger can be adjusted from 45.5 mV to 162 mV where the ratio of the hysteresis width variation to supply voltage is 19.4%. This circuit consumes 10.52 × 7.91 μm2 of silicon area, and its power consumption is only 1.38 µW, which makes it a suitable candidate for low-power applications such as portable electronic, biomedical, and bio-implantable systems.

Weak Inversion Model of an Inverting CMOS Schmitt Trigger

“…Next 𝑉 𝑚,𝑝 is determined, by equating the currents in 𝑀 1 and 𝑀 5 : So we substitute (11) in (9), and finally by solving for 𝑉 𝐿𝐻 the expression in ( 12) is obtained.…”

Subthreshold Modeling of a Tunable CMOS Schmitt Trigger

“…The associate editor coordinating the review of this manuscript and approving it for publication was Paolo Crippa . [27], [28], [29]. This is mainly due to the supply voltage reduction trend, which represents a key design technique in the power consumption optimization of electronic systems [30].…”

“…In 2018, Bastan et al proposed a subthreshold pseudo-differential ST in 0.18µm CMOS process, which consumes 150nW when operating at 0.4V [36]. In 2020, Radfar et al presented a differential ST circuit (0.18µm CMOS process) with tunable hysteresis based on body biasing [28]. The circuit has a tuning range of approximately 110mV , and it consumes 1.38µW with a supply voltage of 0.6V .…”