Prevents electrostatic discharge at input from damaging the transistors in the circuits.
Upper diode drains high current if high positive voltage appears at input. While lower diode drains high current if high negative voltage appears at input. These diodes are reverse biased during normal operation.
Use appropriate switches to demonstrate application of high positive or high negative voltage or normal operation.
The circuit at right is a simple inverter implemented in CMOS configuration.
Blue line is input to inverter after input protection circuit. While green is output of inverter.
Buffer are used at output to increase the output current and thus increase the output driving capability. This helps in fast charging and discharging of output capacitances.
