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Abstract- Portable electronic devices have extremely low power requirement to maximize the battery lifetime. Various device circuit architectural level techniques have been implemented to minimize the power consumption. Supply voltage scaling has significant impact on the overall power dissipation. With the supply voltage reduction, the dynamic power reduces quadratically while the leakage power reduces linearly (to the first order). However, as the supply voltage is reduced, the sensitivity of circuit parameters to process variations increases. CMOS Schmitt trigger design with given circuit thresholds is described. The approach is based on studying the transient from one stable state to another when the trigger is in linear operation. The trigger is subdivided into two sub circuits, each of them is considered as a passive load for the other. This allows the relations governing the deviations of the circuit thresholds from their given values to be obtained. The trigger device sizes are thus determined by the threshold tolerances. Two new Schmitt trigger designs were presented. As opposed to the traditional implementation scheme, the new design approach used two separate inverters for each positive feedback paths. This modification resulted in near independent trip point control by varying the sizing of the respective feedback inverter in the first proposed design. In the second proposed design, the feedback inverters where modified to include two inputs, one from the internal node of the Schmitt trigger and the other being the output node, which resulted in independent control of the trip points by the sizing of the respective two input inverters. Simulations for these structures showed wide trip point control by varying feedback inverters sizing, specifically by the latter modification utilizing two input inverter scheme. The proposed structures also have added advantage of reduced kick back noise. These structures can also have current sourcing and/or sinking voltage controlled transistors at the output of the input inverter, which can shift the hysteresis window without changing its width. Splitting of the inverters for separate feedback paths along with the use of two input inverters are not limited to the present architecture, but can be used in other Schmitt trigger designs making them more favorable to different applications.
Index Terms- BJT-bipolar junction transistor ,CMOS complementary metal oxide semiconductor, LTP-lower trigger point ,UTP -upper trigger point.