Schmitt triggers are electronic comparators which are widely used to enhance the immunity of circuits to noise and disturbance and are inherent components of various emerging applications. These are commonly used in the field of communication and signal processing techniques for improving on and off control, reducing the noise effects in triggering devices, and analogue to digital conversion (Srivyshnavi and Avireni, 2015). A number of other emerging applications include frequency doublers, retinal focal-plane sensors, sub-threshold SRAM, image sensors, pulse width modulation circuits, wireless transponders, FPGA-based system and sensors. Conventional Schmitt triggers, composed of operational amplifiers, suffer from some inevitable drawbacks which are not prominent in CMOS Schmitt triggers. There are two configurations of Schmitt trigger, namely, inverting and non-inverting, as shown in Figure 1 (Kumngern, 2012). Non-inverting Schmitt trigger is the standard circuit that is used in most devices like voltage flower and oscillator. The symbol is a triangle with an input and an output and hysteresis symbol inside the triangle. The hysteresis curve sign differs depending on the type of Schmitt trigger, inverting or non-inverting (Chandra Shaker and Avireni, 2014).
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