Low-cost and Compact Window Comparator Circuit with MOSFET-Resistor Voltage References

A window comparator circuit is utilised for industrial applications and is related to safety systems for the detection of false signals that check the DC signal level from input. The design concept is based on AND logic circuit. Originally, the window comparator comprised two methods including 1) analogue circuit dependent on the transistor oscillation, which is determined by the values of resistance and each input voltage, and 2) window comparator with op-amp or module ICs comprised of two separate comparators and an AND gate. This paper proposed a window comparator with digital logic IC based on the features of digital switching levels with MOSFET-resistor voltage references. The circuit uses a potential voltage divider circuit utilising resistor and N-channel MOSFET, as well as the threshold voltage of CMOS logic IC to build window boundaries. It does not require any additional components since it is a very simple circuit. The circuit can be used in low voltage and fast varying input. The performance was tested and analysed by simulation and experimental results.